According to the invention, the wheelchair is characterized in that it includes means to incline the whole seat structure, and inclining means that are interposed between the chassis and the lifting means and that include at least: a base (65) that is attached to the chassis (1) and that oscillates around a more-or-less horizontal axis, and on which the lifting means are fitted, and a mechanical assistance means that is interposed between the base (65) and the chassis (1) and that is designed to allow modification of the slope of the whole seat structure by rotation of the base (65).