A mixed-flow fan features a housing (42); an impeller (43) journaled rotatably with respect to the housing, and equipped with fan blades (54); a generally cylindrical air conduit (50) defined between the fan housing and the impeller, the fan blades extending into the air conduit in order, during operation, to transport air; an external-rotor motor (75) having an internal stator (100) and an external rotor (81) which includes a tubular ferromagnetic yoke (63) partly embedded in material of the impeller. A cup-shaped yoke (72) fits into a central cavity (68) of the tubular yoke (63) and accommodates a permanent magnet arrangement (66) which interacts with the stator. The tubular yoke (63) and the cup-shaped yoke (72) together serve as a magnetic return path for the external-rotor motor. The structure minimizes damage during final assembly, and simplifies insertion of balancing weights.