The invention relates to an impeller in rotational symmetry. The impeller is penetrated through by a rotation axis, and furthermore in a side view, the impeller continuously projects from a radial outer side to a radial inner side relative to an outer contour. The impeller has impeller blades connected with a base body on a bottom side. The blades form impeller tips facing away from a bottom relative to an extension of the impeller in a direction of a rotational axis. The tips overlap the body, and/or the blades end with a distance to an edge lap of the body at the bottom side by forming a diffuser region. A radius of a maximum extension of the blades lies in a range between 1.5 to 0.6 times of a radius of a maximum extension of the base body in a top view. An independent claim is also included for an electric motor which comprises a rotor, a stator, and the impeller which is driven by the rotor for cooling the electric motor.