Diono Radian 3QXT Review – Safest Car Seat to Go

Diono Radian 3QXT - purple car seat

Diono Radian 3QXT

Overall Rating
4.5/5
Face Rear & Front

The Radian 3QXT sits firmly among the upper echelons of Diono’s premium convertible car seats. Remaining the slim fit and folding design, and the top weight limit (120 pounds) and rear-facing height limit (50 pounds), while implementing a few advanced safety features, the Diono Radian 3QXT is a top contender in the expensive bracket. Like a bull ready to go and a level of protection that is almost unparalleled, the Radian 3QXT is ready to tackle anything thrown its way (i.e. crashes). Read on – we’re unpacking the key things you need to know about the Radian 3QXT.

*Price may change due to e-commerce platform and brand sales promotion.

This post contains affiliate links. As an Amazon Associate, we earn from qualifying purchases. Thank you for your support!

Diono Radian 3QXT Review - A Bull Ready to Go

Pros & Cons

The good and the bad

What is it best for

Who we recommend it for

Value for Money

Is it worth the price tag?

Design

Dimensions, weight, color, etc

Safety Rating

Crash tests, FMVSS213, SIP

Performance

Weight/height limits, airplane, etc

Installation

Install with LATCH or seat belt

Alternatives

Other car seats to consider

1. Pros and Cons

Pros

Cons

2. Who Is It Best For?

Will the Diono Radian 3QXT Be a Good Fit For Your Child and Family?

The Diono Radian 3QXT is an age-agnostic car seat. A rare breed of the all-in-one car seat, the Radian 3QXT is suitable for newborns as small as 4 pounds and for big kids as heavy as 120 pounds, within the top 57.1 inches height limit.

Underlining its versatility, this car seat has a convertible design that can be used as a rear-facing car seat for infants, a forward-facing car seat for toddlers, and a booster seat for older children.

Just like its predecessors and siblings – the Diono Radian series – the 3QXT has a slim fit, foldable, and low-profile design to deliver excellent convenience for both parents and kids. Unlike the cheaper models, though, the Radian 3QXT comes equipped with 8 layers of side impact protection (SIP) and a few other advanced safety features, making it a more reliable machine.

Of course, its 30.4 lb bulk means it’s still by no means well-suited for parents to switch it from one car to another – but for families who need to install multiple car seats in one row or who travel a lot, the Radian 3QXT is the way to go.

3. Value for Money

Is the price tag worth it?

It’s not always easy to label car seats knocking on the door of the $400 mark as ‘value for money’ – but for the Diono Radian 3QXT, I’m willing to make an exception.

This car seat is fantastic value. As I’ll discuss in the Diono Radian 3QX series comparison coming up next, the 3QXT has at most 8 layers of SIP and side impact management pod, yet still brings everything I love about that car seat to the table. More importantly, it’s slightly $30 more expensive but a huge $100 cheaper than the 3QXT+, which has one more feature – Safe+ Anti rebound panel.

As we’ll also see later in the review, the Radian 3QXT performs brilliantly when in the illustrious company of the car seats in its price class. Though the Radian 3QXT is outstripped pretty much across the board by the magnificent Britax One4Life – which, if we’re splitting hairs, is even better for money. The Radian 3QXT is still among the best, though, and if we exclude the Britax One4Life, the Radian 3QXT is my top choice.

If you’re in the market for a performance all-in-one car seat with all the hard-hitting specs we’ve come to expect from the Diono, but at a more accessible price, then this car seat is for you. Don’t be put off by the price tag – the Diono Radian 3QXT is worth every nickel.

Car Seats Comparison Radian 3QX Raidan 3QXT Raidan 3QXT+
Price $399.99 $4499.99 $529.99
Weight limits (lb) RF:5-50 / FF: 22-65 / Booster: 40-120 RF:5-50 / FF: 22-65 / Booster: 40-120 RF:5-50 / FF: 22-65 / Booster: 40-120
Height limits (in) RF:44" / FF: 49" / Booster: 57.1" RF:44" / FF: 49" / Booster: 57.1" RF:44" / FF: 49" / Booster: 57.1"
Rear Facing Weights Up to 50lb Up to 50lb Up to 50lb
Newborn Protection Insert & Harness Pads 3-Stage 4-Stage 4-Stage
Memory Foam Comfort+ Cushion
Safe+ Anti-rebound bar
Side Impact Management Pod -
Safe+ Anti-rebound panel & adjustable calf support - -
Side Impact Protection 6 layers 8 layers 8 layers
Headrest Safe+ 12 position Safe+ 12 Positions Safe+ 12 Positions
Covers Easy remove, machine washable Easy remove, machine washable Premium cut & sew, air-flow mesh panels Easy remove, machine washable
Cup Holder Two XL Two XL Two XL
Fit 3-across
Width (in.) 17 17 17

Middle siblings always seem to be the ones that get lost in a family – sandwiched between the attention-hogging oldest and the creative, fun-loving natures of the youngest. So how does the Raidan 3QXT fare? Does it, too, suffer from the middle-child syndrome, or does it shine in its own right?

In my view, it’s the latter. In fact, the Radian 3QXT manages to share the best traits of both the Diono Radian 3QX and 3QXT+, while still possessing a unique identity of its own. 

Like the 3QX, the 3QXT sports a slim and folding body, with a similarly low profile that affords a more compact feel. However, the 3QXT enhances the safety performance by adding two layers of side impact protection, while also increasing its convenience. 

When it comes to specs and features, though, the 3QXT shares more of its genetic makeup with the Diono Radian 3QXT+ than the 3QX. Sporting a similar level of size limit as its gigger bro – but shaving off a huge slice of the 3QXT+’s high price – the 3QXT is also able to deliver better convenience, as well as fold in a way that’s more portable (and, frankly, just makes a lot more sense). 

It’s easy to imagine Diono starting with the intention of making a smaller, lighter version of 3QXT+. Instead, they upgrade it. 

Because ultimately, the 3QXT takes most of what the 3QXT+ does well, and decreases the price, while also serving as a clear improvement on the 3QX. Though there are still question marks around whether the 3QXT is the best in its calls (particularly with the Britax One4Life on the installation). It can certainly make the case of being the overall best Diono package on the market, though.

4. Design

Dimensions and Width

The Diono Radian 3QXT car seat has the following dimensions:

  • Width: 17 inches
  • Depth: 16 inches
  • Height: 28.5 inches

From its width of only 17 inches, we know that the Radian 3QXT is a narrow and slim fit. Actually, it’s one of the narrowest car seats on the market (there are still some narrower 16.75-inch car seats.). The 17-inch width makes it a good choice for families who need to fit multiple car seats in a single row or who have limited space in the back seat. The Radian 3QXT can fit three across in most mid-sized vehicles, and even in some smaller vehicles.

But its 28.5-inch height might be a problem for fitting in small cars, especially when it is fully reclined. It measures approximately 31 inches from the front of the car seat to the back of the car seat, making it take up a bit more space from the front seat passengers.

Portability

Constructed with a metal frame, the Diono Radian 3QXT is a bit heavy, weighing 34.2 pounds. You’ll find it’s even heavier than most all-in-one and convertible car seats on the market, as heavy as the swivel car seats. The positive point is that this will let parents think they’re solid and strong to deliver protection.

Commonly, car seats weighing more than 30 pounds are not that portable and it’s not as convenient as those lightweight convertible car seats to switch between vehicles. The Radian 3QXT (and other Diono Radian car seats) is a game changer. 

They are heavy, but they have a high score in portability.

They are designed to be foldable, which makes them even more portable and convenient than most car seats for travel. The car seat can be folded up for easy storage and transportation, and it comes with a carry strap that makes it easy to carry the car seat like a backpack with you when you’re on the go.

Foldable design for best portability

How to unfold and fold Diono Radian 3QXT?

1. Place the car seat on its back on a flat surface and unfasten the red carry strap from the bottom. Be sure the harness adjuster moves freely and is not locked within the bottom of the seat. 

2. Rotate the bottom until you hear it “click”, this confirms the car seat is locked for use. 

3. Check proper operation — Pull harness adjusting strap until harness begins to tighten. If it does not tighten freely, check the belt path on the back of the seat bottom is clear from obstruction. To fold the seat, release the levers as shown and repeat the above steps in reverse. 

4. Tuck the red strap through the harness slot and store it behind the cover. 

5. To fold, push the lever shown and secure with red strap.

Cup Holder - Two

The Diono Radian 3QXT car seat comes with two cup holders that can be attached to either side of the car seat. The cup holders are designed to be large enough to accommodate most standard-sized cups, bottles, and sippy cups, up to 10 ounces in size.

They are also deep enough to securely hold items, preventing them from falling out or spilling while the car is in motion. This can be especially helpful for families who like to bring drinks or snacks in the car, as it provides a convenient and secure place to store these items.

In addition to holding drinks, the cup holders can also be used to hold small toys or other items that a child may want to have within easy reach while in the car.

However, it’s important to note that the cup holders are not designed to hold heavy or sharp items or to be used as storage compartments for larger items.

Headrest and Harness - 12 Positions

The Diono Radian 3QXT car seat has 12 headrest positions, which is more than most other car seats on the market. The headrest can be easily adjusted up or down to accommodate a child’s growth and ensure a comfortable and safe fit.

The headrest is an important safety feature of any car seat, as it helps to protect a child’s head and neck in the event of a crash. A properly positioned headrest can prevent the child’s head from moving too far forward or to the side, which can help to reduce the risk of injury.

In addition to the safety benefits, the 12 headrest positions of the Diono Radian 3QXT also provide added comfort for the child. The headrest can be adjusted to the perfect height, ensuring that the child’s head is supported and comfortable during long car trips.

Reclines - 4 Positions

The Diono Radian 3QXT car seat has five different recline positions, which can be adjusted based on the age, size, and comfort level of the child. The recline positions are adjusted using a lever located at the front of the seat.

To adjust the recline, first, loosen the harness by pressing the harness release button and sliding the harness adjuster strap forward. Then, lift the lever at the front of the seat and adjust the seat to the desired recline position. The recline positions range from fully upright to a full recline for infants.

It’s important to ensure that the seat is properly reclined to provide both comfort and safety for the child. For rear-facing positions, a more reclined position is recommended for younger infants to prevent their head from flopping forward, while a more upright position is recommended for older babies and toddlers. For forward-facing positions, a more upright position is recommended for older toddlers and children who have good head control.

It’s also important to check the vehicle owner’s manual for the recommended recline position when installing the car seat. The correct recline angle can help ensure that the car seat functions properly and provides the necessary protection in the event of a crash.

Infant Accessories

The Diono Radian 3QXT car seat is compatible with a variety of infant accessories, which can help to provide additional support and comfort for infants.

One of the most important accessories is the infant insert, which is designed to provide extra support for newborns and younger infants. The infant insert consists of a removable cushion and padded headrest, which can be used to ensure that the baby’s head and neck are properly supported and that they are positioned correctly in the car seat. The infant insert is adjustable and can be removed as the baby grows and requires less support.

Another accessory is the plush newborn body support cushion, which provides additional support for the baby’s head, neck, and body. This cushion is made from soft, breathable materials and can be easily removed for cleaning.

In addition to these accessories, the Diono Radian 3QXT car seat also includes a removable cup holder, which can be attached to either side of the seat for convenience.

It’s important to note that while these accessories can provide additional support and comfort for infants, they should only be used as directed and in accordance with the car seat manual. Improper use of infant accessories can affect the safety of the car seat and increase the risk of injury in the event of a crash.

Padding

The Diono Radian 3QXT car seat has a padded seat and backrest, which provides additional comfort and support for the child. The padding is made from high-quality materials and is designed to be both soft and durable.

The exact thickness of the padding can vary depending on the specific area of the car seat. For example, the seat cushion and headrest have a thicker layer of padding, while the backrest has a thinner layer of padding to allow for proper fit and support.

The padding is made from a variety of materials, including foam and polyester fiber, which are both soft and durable. The car seat cover is made from a breathable and machine-washable fabric that is both comfortable for the child and easy to clean.

Overall, the padding in the Diono Radian 3QXT car seat is designed to provide both comfort and safety for the child. The padding helps to absorb the force of a crash, reducing the risk of injury, while also providing a comfortable and supportive seating surface for the child during everyday use.

5. Diono Radian 3QXT Safety Rating and Crash Tests

Is it safe to use Diono Radian 3QXT?

The Diono Radian 3QXT car seat is designed with safety as a top priority and has been thoroughly tested to ensure that it meets or exceeds all applicable safety standards. It is certified for use in the United States by the National Highway Traffic Safety Administration (NHTSA) and in Canada by Transport Canada.

The Radian 3QXT has undergone rigorous crash testing to ensure its safety in the event of a collision. It has been tested using both front and side-impact crash simulations, and it has been designed to meet or exceed all federal safety standards for car seats.

Additionally, the Radian 3QXT features Diono’s Safe+ engineering technology, which includes a number of safety features such as a Safe+ steel anti-rebound bar, Safe+ stop energy-absorbing harness, and Safe+ side impact protection. These features work together to provide enhanced safety and protection for children while in the car.

It’s important to note that while the Radian 3QXT has passed all applicable safety tests and meets or exceeds all safety standards, no car seat can guarantee complete safety in the event of a collision. However, by choosing a car seat that has been thoroughly tested and designed with safety in mind, parents can have peace of mind knowing that they are doing everything possible to protect their child while on the road.

Side Impact Protection - 8 Layers

The Diono Radian 3QXT car seat features Safe+ side impact protection, which is designed to provide enhanced safety in the event of a side-impact collision. The Safe+ side impact protection system includes eight layers of side impact protection to help minimize the forces of a crash and protect a child’s head, neck, and torso.

What are the eight layers of SIP? They include:

Aluminum-reinforced headrest: The headrest is reinforced with aluminum to help absorb and disperse energy in the event of a collision.

EPS foam: The Radian 3QXT features EPS foam throughout the seat, including in the headrest, seat back, and sides, to provide additional energy absorption and protection.

Safe+ shell: The car seat’s Safe+ shell is made of automotive-grade high-strength steel and provides a strong and protective frame that helps to reduce side-impact forces.

Safe+ sidewalls: The Radian 3QXT’s Safe+ sidewalls are made of high-density plastic and are designed to provide additional energy absorption and protection in the event of a collision.

Radian 3QXT’s Safe+ engineered core: This is a layer of high-density foam that is located in the center of the car seat, which provides additional structural support and helps to reduce side-impact forces.

Safe+ side impact pods: The Radian 3QXT features two Safe+ side impact pods on either side of the car seat, which are designed to absorb and disperse energy in the event of a collision.

Safe+ angle adjuster: This is a removable wedge that can be used to adjust the angle of the car seat in the vehicle, providing additional protection in the event of a side-impact collision.

Safe+ steel anti-rebound bar: The car seat comes with a Safe+ steel anti-rebound bar that attaches to the back of the car seat, providing additional stability and protection in the event of a crash.

These layers work together to minimize the forces of a crash and help keep children safe while riding in the car.

6. Performance

Weight and Height Limits

The Diono Radian 3QXT car seat is designed to be used in three different modes: a rear-facing harness, a forward-facing harness, and a booster seat. The height and weight limits for each mode are as follows:

Rear-facing harness

For children weighing between 5 and 50 pounds, and up to 44 inches in height. This weight and height limit is higher than many other convertible car seats on the market, which typically have a rear-facing weight limit of 40 pounds or less.

The extended rear-facing weight and height limits of the Radian 3QXT make it an excellent choice for parents who want to keep their child rear-facing for as long as possible. The American Academy of Pediatrics (AAP) recommends that children remain rear-facing until at least 2 years of age, or until they reach the highest weight or height allowed by their car seat.

The extended rear-facing capability of the Radian 3QXT allows children to remain rear-facing for longer than the minimum recommended by the AAP, which can provide additional safety benefits.

Forward-facing harness

For children between 22 to 65 pounds, and up to 49 inches in height. Once a child reaches the weight or height limit for rear-facing, they can be turned forward-facing in the car seat. The forward-facing weight and height limits are similar to those of other convertible car seats on the market.

Once a child has outgrown the rear-facing weight and height limits, they can be turned forward-facing in the Radian 3QXT car seat. It’s important to note that the AAP recommends that children remain rear-facing for as long as possible, up to the highest weight or height allowed by their car seat. This is because rear-facing car seats provide better protection for a child’s head, neck, and spine in the event of a crash.

When a child is turned forward-facing, the car seat should be installed in the vehicle using the tether strap and the vehicle’s seat belt or lower anchors. The Radian 3QXT car seat features an adjustable 5-point harness that can be easily adjusted to fit a growing child. The car seat also features energy-absorbing foam and a reinforced steel frame for added safety in the event of a crash.

Booster mode

For children between  40 to 120 pounds, and up to 57.1 inches in height. This makes it a versatile car seat that can be used as a child grows and transitions through different stages of car seat safety.

When using the Radian 3QXT as a booster seat, the vehicle’s seat belt is necessary to secure the child in the car seat. The booster seat features adjustable headrest and backrest positions to provide a comfortable and secure fit for a growing child.

It’s important to note that the AAP recommends that children remain in a booster seat until they are big enough to properly fit in a vehicle seat belt, which is usually when they reach a height of 4 feet 9 inches and are between 8 and 12 years old. The booster seat helps to position the vehicle’s seat belt properly on a child’s body to provide the best possible protection in the event of a crash.

Parents should always refer to the car seat’s manual for specific weight and height limits, as well as installation instructions and safety guidelines. It’s also important to ensure that the car seat is installed correctly and securely in the vehicle and that the child is properly secured in the car seat according to the manufacturer’s instructions.

Stage / Modes

The Diono Radian 3QXT car seat is a convertible car seat that can be used in three different stages, making it a versatile option for parents looking for a car seat that can grow with their children.

Rear-Facing Stage: In this stage, the car seat is installed in a rear-facing position, which provides the best protection for a child’s head, neck, and spine in the event of a crash. The Radian 3QXT car seat features adjustable headrests and recline positions to provide a comfortable and secure fit for a growing child. The anti-rebound bar enhances its protection in this mode, making the Radian 3QXT a safe car seat to use.

Forward-Facing Stage: This is the second stage and the car seat is turned forward-facing and is installed using the vehicle’s seat belt or lower anchors, along with the tether strap. The Radian 3QXT car seat features an adjustable 5-point harness and energy-absorbing foam to provide added safety in the event of a crash.

Booster Stage: The third stage is the booster stage. In this stage, the car seat is used as a booster seat, with the vehicle’s seat belt securing the child in the car seat. The Radian 3QXT car seat features an adjustable headrest and backrest positions to provide a comfortable and secure fit for a growing child.

The three stages of the Diono Radian 3QXT car seat provide a complete car seat solution for children from birth up to 120 pounds. Parents should always refer to the car seat’s manual for specific weight and height limits, as well as installation instructions and safety guidelines. It’s also important to ensure that the car seat is installed correctly and securely in the vehicle and that the child is properly secured in the car seat according to the manufacturer’s instructions.

Age Range

While age can be a helpful guideline, weight, as well as height, are more important factors when determining which stage of the Diono Radian 3QXT car seat a child should be using.

Check the weight and height limits for each stage of the car seat above and here we’ll explain what the approximate age range for each stage according to the height and weight limits.

Rear-Facing Stage: 4-50 lbs/ 44″. Different from infants outgrow the height limit of an infant car seat. Most children will outgrow the rear-facing stage by weight before reaching the height limit for Radian 3QXT. That means, the rear-facing can be extendable for kids around three years old. See also car seats for 3 year olds.

Forward-Facing Stage: 22-65 lbs/ 49″. Most children will outgrow the forward-facing stage by weight before reaching the height limit.  And kids around 5 years old can still use the 5-point harness for protection in this stage. See also car seats for 5 year olds.

Booster Stage: 40-120 lbs/ 57.1″. Most children will outgrow the booster stage by height before reaching the weight limit. That means the car seats can be used for kids around 8 years of age, which is,  in most US states’ car seat laws, the minimum age requirement to stop using a car seat.

Airplane

Is Diono Radian 3QXT FAA approved for use on a plane?

Yes, the Diono Radian 3QXT car seat is certified by the Federal Aviation Administration (FAA) for airplane use. This means that the car seat has been tested and approved for use on airplanes, and it meets all FAA safety requirements.

To use the car seat on a plane, parents should follow the airline’s specific guidelines for installing and using the car seat. Generally, the car seat must be used in a forward-facing position, and it must be secured to the plane’s seat using the aircraft’s seat belt.

Additionally, parents should ensure that their car seat is labeled with the “This restraint is certified for use in motor vehicles and aircraft” statement to indicate that it is FAA approved.

It’s important to note that not all airlines allow the use of car seats on their planes, and some may have specific requirements or restrictions. Parents should check with their airline before traveling to ensure that they can bring and use their Diono Radian 3QXT car seat on the plane.

Lifespan

How long is Diono Radian 3QXT car seat good for

The Diono Radian 3QXT car seat does have an expiration date, as do all car seats. It has an expiration date of 10 years from the date of manufacture. Typically, the expiration date is typically printed on a sticker or label located on the car seat itself. 

Car seats expire because the materials and components used in them can degrade over time, and they may no longer meet the required safety standards. Additionally, new safety technologies and features may be developed that make older car seats less safe by comparison.

It’s important for parents to be aware of their car seat’s expiration date and to replace it once it has expired, even if it still looks to be in good condition. Continuing to use an expired car seat can put a child at increased risk of injury in the event of a crash.

You need to do a simple calculation to get the exact expiration date of all Diono car seats by using the date of manufacture and the lifespan.

Warranty

The Diono provides a one-year limited warranty for the Radian 3QXT car seat, starting from the date of purchase. The warranty covers defects in materials and workmanship under normal use and service.

Additionally, if you register your car seat on the Diono website within 30 days of purchase, you can extend the warranty to cover your car seat for up to ten years. This extended warranty covers the same defects in materials and workmanship as the standard one-year warranty.

It is important to note that the warranty does not cover damage caused by misuse or abuse of the car seat, normal wear, and tear, or damage caused by accidents or collisions.

7. Diono Radian 3QXT Installation

Before starting to install the car seat, you may where to put it. The center of the back seat is probably the safest position to install a car seat.

If possible, install the car seat on that spot. If that seat is not applicable for a proper installation, for example lacking a shoulder belt, either seat on the side would be safe. You may choose any of them based on your family’s and kid’s needs.

Diono Radian 3QXT Rear-facing Installation

  • Rear-facing Installations Tips for 5–50 lb (2.3–22.7 kg) 
  • Choose LATCH, lap belt, or lap-shoulder belt.
  • LATCH can be used for installation for infants between 5–35 lb (2.3–15.8 kg), DO NOT install by this method for a child weighing more than 35 lb (15.8 kg).
  • You should reinstall with a vehicle belt for weights between 35–50 lb (15.8–22.7 kg). 
  •  
  • Infants who weigh less than 22 lb (10 kg) and are under 1 year old, MUST use this car seat rear-facing. 
  • Place the car seat rear-facing in the vehicle back seat. 
  • Make sure the LATCH strap or vehicle seat belt is routed through the rear-facing belt path marked with the blue text and rear-facing illustrations. 
  • Install this car seat tightly in your vehicle. The car seat should not move at the rear-facing belt path location by more than 1 in. (2.5 cm) from side-to side, front-to-back. 
  • If using a lap belt only, refer to your vehicle’s owners manual for installation advice. 
  • Harness straps MUST be at or just below the top of your child’s shoulders. 
  • Place the chest clip at armpit level. 
  • Never place a rear-facing car seat in the front with an airbag on.

Diono Radian 3QXT Forward-facing installation

  • Choose LATCH, lap belt, or lap-shoulder belt.
  • LATCH can be used for 22–40 lb (10–18 kg). DO NOT install this method for a child weighing more than 40 lb (18 kg). Reinstall with vehicle belt for weights between 40–65 lb (18–29.5 kg). 

  • NOTE: If the child is UNDER 40 LB (18 KG), install the Diono SafeStop by following the instructions on page 59 before proceeding. IMPORTANT: The SafeStop will need to be removed once the child reaches 40 lb (18 kg).
  • NOTE: If the child is OVER 40 LB (18 KG), go to step 1 of Installation using a Lap/Shoulder With 5-Point Harness. IMPORTANT: If the child is OVER 25 LB (11.3 KG), lower the adjustable bottom by following the instructions on page 42. 
  • NOTE: For forward-facing installations using a LAP BELT ONLY with NO top tether anchor point available, you MUST install the Diono Lap Belt Cushion by following the instructions on page 60 before proceeding; otherwise proceed to the next page.
  • Lift the bottom bar up and over the inside channel toward the seat bottom to release. Confirm locked. Make sure the LATCH strap or vehicle seat belt is routed through the forward-facing belt path marked with the red text and forward-facing illustrations. Install this car seat tightly in your vehicle. The car seat should not move at the forward-facing belt path location by more than 1 in. (2.5 cm) from side–to– side, front–to–back. If using a lap belt only, refer to your vehicles owners manual for installation advice. Harness straps MUST be above the top of your child’s shoulders. Place chest clip at armpit level. The American Academy of Pediatrics (AAP) and NHTSA recommend that children be rear-facing until they reach the maximum rear-facing height and weight. This car seat can remain rear-facing up to 50 lb (22.7 kg).

Diono Radian 3QXT Booster Installation

  • For 40–120 lb (18–54 kg) 
  • Use ONLY the vehicle lap/shoulder belt system when restraining the child in this booster seat. DO NOT USE A LAP BELT ONLY!
  • Make sure the vehicle seat belt can properly retract before each use.
  • If a 5-Point harness is installed, please review the harness removal section. The 5-Point harness MUST be removed to use this seat in booster mode. 

1. Place the child in a seat with their back flat against the back of the booster seat. 

2. Slide vehicle’s lap/shoulder belt through booster belt guide over seat . 

3. Buckle the vehicle lap/shoulder belt. Be sure the lap/shoulder belt lies across your child’s shoulders, between the neck and edge of the shoulder. Be sure the lap portion of the vehicle seat belt goes under the side nubs and 3 the belt lies low across your child’s hips.

Diono Radian 3QXT Car Seat Manual

You should always read the user manual before starting to install and use it for riding your child. 

The Diono Radian 3QXT manual is stored in a small storage slot on the back of the car seat, but you can always find the online user manual on its official website, or download the PDF here.

8. Specifications

Brand 
BrandDiono
Type 
Suitable forNewborns, toddlers, and big kids
PositionsRear-facing and forward-facing
Design 
Portability (1-10)8. Slim but a bit heavy duty
Weight (pounds)34.2
Weight limits (lb.)4-50 for rear-facing, 22-65 for forward-facing, 40-120 for booster
Height limit (inch)44” for RF, 49” for FF, and 57.1″ for booster
Dimension17 x 16 x 28.5″ WDH
Cup holderTwo XL
Performance 
Age RangeBirth-8 years or older
Stage1st, 2nd, 3rd
InstallationLATCH and seat belt
Headrest Positions12
Reclines5
AirplaneYes
Lifespan10 Years
Extra FeaturesFit 3 across, folding design for portability

Diono Radian 3R vs 3RX vs 3RXT vs 3QX vs 3QXT

Car Seats Comparison Radian 3R Radian 3RX Raidan 3RXT Raidan 3QX Radian 3QXT
Price $199 $269 $329 $369 $399
Weight limits (lb) RF:5-50 / FF: 22-120 RF: 5-50 FF: 22-120 RF: 5-50 FF: 22-120 RF: 4-50 FF: 22-120 RF: 4-50 FF: 22-120
Rear Facing Weights Up to 50lb Up to 50lb Up to 50lb Up to 50lb Up to 50lb
Newborn Protection - - 2-in-1 Advanced 3-in-1 Advanced 4-in-1
Safe+ Engineering - - -
Head Support - 12 Positions 12 Positions Safe+ 12 Positions Safe+ 12 Positions
Cup Holder -
Fit 3-across
Width (in.) 17 17 17 17 17

*About the height limit for rear-facing: The top of the head must be 1” (2.5 cm) below the headrest adjustment lever.

9. Alternatives

What other all-in-one car seats should you consider?

Graco SlimFit LX 3-in-1 Car Seat

Graco SlimFit3 LX

Why is it better than the Diono Radian 3QXT?
Why is it worse than the Diono Radian 3QXT?
Britax One4Life ClickTight All-In-One Car Seat

Britax One4Life

Why is it better than the Diono Radian 3QXT?
Why is it worse than the Diono Radian 3QXT?