An occupant protection system, in particular for motor vehicles, is provided with at least one distance measuring device (12) for continuously monitoring the sitting position of an occupant (1) belted to a vehicle seat (4) by means of a safety belt (3), in relation to at least one air bag module (6) provided for this vehicle seat (4), wherein the safety belt (3) is passed over the chest portion of the occupant (1) and the distance measuring device (12) includes one or more transmitting and receiving devices (13, 14, 14a, 14b) for reflectable beams, for example light, ultrasonic or radar beams, as well as a method for continuously monitoring the sitting position of the occupant (1). Preferably, the distance measuring device (12) is designed for detecting one or more reference points or regions (7) of the safety belt (3) in the chest portion and the safety belt (3) is designed to reflect radiation in spots or sections for forming the reference points or regions (7) for distance measurement (12).