A process and device are disclosed for preventing a vehicle from colliding with an obstacle during parking. The object of the invention is therefore to ensure that a collision can be reliably avoided without any additional intervention of the drive. In a device with at least one sensor for generating signals which represent the distance between the vehicle and an obstacle, the signals are processed in an evaluation unit. When at least one distance-representing signal falls below a limit value, a warning signal is generated. This warning signal drives a control valve which generates a pressure difference between the working chamber and the vacuum chamber in a brake booster when the warning signal is generated. This pressure difference causes the braking pressure to rise in the wheel brake cylinder and therefore slows the vehicle down to a standstill.