A method and a device for detecting the occupancy state of a seat, e.g., in a vehicle, and for use in activating a restraint mechanism allocated to the seat, as a function of the occupancy state, are provided. With the aid of an image recording system, a 3D image of the seat is recorded and evaluated with respect to the occupancy state, and optionally also with respect to the type of the occupancy. For the evaluation, a 3D pattern is drawn upon, which is available externally or which is able to be generated internally in an initialization step. A hierarchically constructed evaluation also permits, after determination of an occupancy state, a classification with respect to the type of the respective occupancy.