The seat surface of a chair of a chair lift can be pivoted with the aid of a pivot mechanism. Thus, the seat surface can, while a passenger is sitting thereon, be pivoted in such a way that it extends so as to descend, or descend more markedly, toward the rear edge of the seat part. Passengers enter automatically, and independently of their size and sitting position on the chair, into a stronger, stable back position, thereby reliably counteracting slipping in the direction of the front edge of the seat part and thus slipping-through between the seat surface and transverse hoop.