A blind spot sensor system detects and/or classifies objects in a defined monitoring region of a motor vehicle. The blind spot sensor system contains a first device for emitting a first radar beam, and a second device for emitting a second radar beam. The radial visual range of the first radar beam (beam I) inclines counter to a direction of travel of the motor vehicle and the radial visual range of the second radar beam (beam II) is oriented in an substantially vertical manner in relation to the direction of travel such that the visual range of the radar beams (I and II) at least partially overlap and cover, substantially, the monitoring region. At least the first radar beam (beam I) can be actuated in a CW modulation mode and in a FMCW modulation mode. The blind spot sensor is used in vehicles, for example for assisting in lane changing.