An apparatus for warning a vehicle driver about an object, including: a) a sensor device having a detection area (DA) extending from a front DA, in front of a vehicle, including the front DA, to a rear end of a side DA, laterally from one vehicle side and whose length corresponds to no more than the vehicle length, the sensor device detecting an object, b) a control device to evaluate the sensor signals for objects and defines a warning area (WA) that is dynamically alterable (DyA) based on the vehicle speed, the WA being alterable within the side DA between a non-zero minimum/maximum WA, c) a warning device generating a warning signal for a detected object, d) the sensor device being such that the DA continues from the side DA into a rear DA behind the vehicle rear, including the rear DA, e) the control device expanding the DyA WA.