The invention relates to a method for detecting incorrectly parked vehicles (15). Information on available parking areas (8, 8a) and areas (9) which are not available for parking is provided in the form of a digital parking space map. The information on areas (9) which are not available for parking comprises coordinates, in particular GPS coordinates, and an expected length of the area. According to the invention, the length of an area (9) which is not available for parking is detected by a vehicle (2) searching for a parking space, and if the detected length deviates from an expected length, an incorrectly parked vehicle (15) is detected.