A method of balancing an electronically driven air blower unit comprising a radial blower with a high-speed electronically commutated d.c. motor which drives the blower and which is of external rotor design, utilizing a balancing device into which the completely mounted air blower unit (1) can be inserted, without housing lid, and with which electrical contact (101, 102, 103; 201, 202, 203) can be made. The balancing device is provided with a control device for the motor (3, 4, 5) of the air blower unit and with a device (9) for bridging the motor electronics (10) of the air blower unit (1) itself. In order to drive the part to balanced of the air blower unit, its electromechanical transducer (3, 4, 5) is used, which for this purpose is actuated by the control device provided in the balancing device. The balancing process is essentially carried out in two compensation planes which are spaced axially from one another and are parallel with one another. This takes place on the one hand in a first compensation plane in the plane of the radial blower with possible erosion of material, and on the other hand in the second compensation plane, which lies opposite in the region of the end side of the external rotor (5), with possible attachment of material.