Abstract: The invention relates to a device (1) for ventilating a crankcase of an internal combustion engine, comprising a ventilation line leading from the crankcase to the suction line of the internal combustion engine, an oil-mist separator (2) for separating the oil parts from the blow-by-gases containing the oil-mist from the crankcase is arranged in the path thereof. Also, said device (1) comprises a pump (3) which is arranged upstream of the oil-mist separator (2) and which is used to produce a negative pressure. The invention is characterised in that the oil-mist separator (2) and the pump (3) are embodied as connected modules thus providing a particularly compact structure.