A folding wheelchair (1), which can be folded up and unfolded between an operating position and a folded position, has a frame (2) comprising two side portions (21), a seat (3) and a folding mechanism (4). The folding mechanism (4) comprises two coupling connections (43), two pivoting connections (42) and a cross-strut (41) with two bars (411) crossing at a pivot point (412). A first longitudinal end (4111) of each of the two bars (411) of the cross-strut (41) is mounted rotatably on one of the two side portions (21) of the frame (5) via one of the pivoting connections (42). A second longitudinal end (4112) of each of the two bars (411) of the cross-strut (41) is mounted releasably on the other of the two side portions (21) of the frame (5) via one of the coupling connections (43). The two bars (411) of the cross-strut (41) at the pivot point (412) are pivotable relative to each other. A distance between the side portions (21) of the frame (5) can be modified if the second longitudinal ends (4112) of the two bars (411) of the cross-strut (41) are released from the side portions (21) of the frame (5). The bars (411) of the cross-strut (41) are pivoted relative to each other about the pivot point (412). The cross-strut (41) extends from the first longitudinal ends (4111) of the two bars (411) to the second longitudinal ends (4112) of the two bars (411) in a cross-strut direction (8) which, in the operating position, extends substantially along the seat (3). The pivoting connections (42), the coupling connections (43), or the pivoting connections (42) and the coupling connections (43), can be offset towards the two side portions (21) of the frame (2) along the cross-strut direction (8).
