Abstract: A mattress extension system for providing an extended mattress support surface adjacent to one or both sides of a treatment mattress such as a low air loss mattress or the like. The preferred embodiment of the present invention contemplates a base board having a width equivalent to the total width of the support surface desired, with first and second mattress pads engaged to opposing edges of the base board so as to form a compartment therebetween to receive the treatment mattress. The base board may further be hinged in one or more places along its width for providing adjustable patient support, or for storage or transportation.