Abstract: A seat assembly for vehicles such as automobiles or passenger trains comprises a child-sized seat which is shiftable between an extended position for use atop an adult-sized chair, and a retracted position recessed within a chamber of the adult chair when use of the latter is instead desired. The child seat is comprised of a molded, generally U-shaped base and back which are pivotally interconnected to enable the child seat to assume a low profile, folded disposition when the child seat is recessed within the chamber of the adult chair. A cushioned panel, pivotally coupled to the back of the adult chair, rests on the folded child seat when the latter is in its retracted, non-use position for comfortable support of an adult using the adult chair. A lever mechanism and guide track arrangement provide proper movement of the child seat between its extended position for use and its recessed, non-use position.