An internal combustion engine, especially for motor vehicles, includes separate oil return and vent channels extending between a crank space of a cylinder crankcase and a valve-actuating space formed by a cylinder head and a cover. For the defined and separate guidance of the media passing through the oil return channels and vent channels, the oil return channels are arranged at a distance to the vent channels and the vent channels are connected to an air guide device inside of the valve-actuating space.