Abstract: A child's booster seat comprises an inflatable seat member having a primary base chamber, two opposed side chambers and a back chamber upstanding from the base chamber. An inflatable secondary base chamber is located below the primary base chamber to support the seat member thereon, the secondary base chamber being selectively inflatable to determine the height of the seat member relative thereto, restraining means being provided for retaining a child in the seat member, and securing means being provided for attaching the booster seat to a supporting chair.