An improved passenger vehicle with an adjustable seat is described. The seat is provided with a frame which includes a back subframe having a backrest cushion, a seat subframe with a seat cushion and a fastening subframe. The fastening subframe is suitable for mutually fastening the back subframe to the seat subframe, and/or is suitable for attaching one of the back subframe and seat subframe, or both, to a floor of the passenger vehicle. The frame can be adjusted between a seating position and a sleeping position. The upper side of the seat cushion in the sleeping position is situated below the upper side of the seat cushion in the seating position.