This is a review of the Diono Radian R120 three-in-one car seat. A three-in-one car seat, like a convertible, first rear-faces, then forward-faces with a five-point harness once rear-facing is outgrown, then has an option to use as a belt-positioning booster.



  • Rear facing weight limits: 5-45 lbs.
  • Rear facing height limits: 57 inches or less and at least one and a half inches of shell over the top of the head
  • Forward facing age and weight limits: One year of age and 20-80 lbs.
  • Forward facing height limits: 57 inches or less, ears below top of restraint
  • Booster minimum limits: 50 lbs., 40 inches tall, and shoulders above the fourth (4th) set of harness slots
  • Booster maximum limits: 120 lbs., ears below top of restraint


  • Steel-alloy frame and aluminum reinforced sides
  • SafeStop load limiting device on harness for forward-facing children under 40 lbs. when using the top tether
  • EPS foam panels on all sides


  • Rear-facing tether capability
  • SuperLATCH may be used, according to manufacturer, to install up to full 80 lb. weight limit in all vehicles manufactured on or after Sept. 1, 2005
  • Two forward-facing recline positions
  • Sits low on vehicle seat
  • Fits three-across in a mid-size vehicle
  • Rubber bottom grips


  • Add up to four cup holders (one included)
  • Folds flat for travel and storage
  • Eight year life as a harnessed seat, ten year life as a booster
  • Cover is machine washable and dryable


  • Infant full-body support cushions
  • Memory foam padding
  • Five shoulder and three buckle positions for harness
  • Expandable sides
  • Longer seat bottom for leg support


Certified for aircraft use in harness mode. 

MSRP (US) $309.99

Buy it at now!

There are no NHTSA Ease-of-Use or IIHS booster fit ratings available for this seat at this time.

CarseatBlog’s Professional Review

Instruction Manual

TheCarseatMom’s Quick Review:

The Diono Radian R120 is the next-generation successor to the Sunshine Kids Radian 80SL. This seat has a 45 lb. weight limit and tall shell, allowing the maximum rear-facing weight of any seat currently on the North American market and extended time rear-facing by height, too. This seat is a step down in price from the Radian RXT, and lacks the adjustible headwings. Like all the Radian seats, this seat allows use of the tether while rear-facing; this may provide additional stability in some types of crashes and, in the case of the Radians, may be used to adjust the recline angle for a younger child. The seat folds for travel and storage convenience, but is made with a metal frame, which makes it a very heavy, solid seat. This seat is large front to back, although narrow side-to-side, and may take up too much room in some vehicles; an "Angle Adjuster" accessory (sold separately) is now available to correct potential problems of overrecline and to allow the seat to take up less space by letting older children sit more upright. Diono states that in vehicles manufactured on or after Sept. 1, 2005 (usually 2006 model year), the SuperLATCH connectors may be used to the maximum weight limit of the harness; however, some vehicle manufacturers do not agree, and both manufacturer's positions should be considered when choosing an installation method. There are some incompatibilities with SuperLATCH install due to the angle the strap adjuster rests at causing it to loosen in some vehicles; check the installation carefully when using the lower anchors on this seat to ensure it does not loosen.

The booster belt guides on this seat are not adjustible. While positioning of the belt tends to be overall good, there may be some issues with slack not retracting once introduced, and fit is not adjustible, so caution must be taken to make sure the booster mode is used properly. The high minimum limits on booster use mean that some children may outgrow it by height before they reach the minimum weight, as well, and the usage issues may mean this is not the best choice for an everyday booster. Overall, this seat is an excellent choice for larger, taller or heavier children to rear-face longer, and the high limits on the harness allow use beyond outgrowing it rear-facing, though most children will outgrow the seat by height well before the maximum weight is reached; the booster, while it does seem to position the belt well, has issues that may lead to another, dedicated belt-positioning booster being a better choice for children who have outgrown the harness and need a high-backed belt-positioning booster. While there are some installation issues in some vehicles, many of them are not true incompatibilities, and the seat can be installed properly in most cars both rear- and forward-facing, though sometimes at the expense of space in the front passenger seat. This seat may also be especially useful for those who do a lot of plane travel with a forward-facing child, as it is known to install well on airplanes in forward-facing harness mode, and to allow use of the tray table.