A support cushion for children's furniture defines a seat cushion area and a back cushion area and has a seating surface that extends over those areas and is contoured to provide positional support and comfort for a child seated on the cushion. The cushion preferably is a one-piece closed cell foam moulding which is flexible to permit variation in the relative angular orientation between the seat cushion and the back cushion area. The seat includes a raised transverse barrier that is spaced forwardly of the rear of the seat for controlling rotation of the pelvis of a child. The cushion further includes a pair of side support pads that extend forwardly from respectively opposite sides of the back to locate against the trunk of a child and cushion against side-to-side movement.