Abstract: A sitting posture correction device for placement between a backrest and the back of a user. The device comprises an inflatable bladder which is generally spherical in shape when fully inflated and a flexible, substantially rectangular cover for the bladder forming a pocket and adapted to contain the bladder, when the latter is partially inflated, in the pocket. During use of the device, the bladder is located within the cover, is partially inflated, and is free to shift and change its shape within the cover.