The invention relates to a drive unit (12) for vertical or horizontal movement of a component (7) of a diagnostic X-ray device (1), comprising a motor and gear unit (14), a pulley (10) mounted on a drive shaft (13) of the motor and gear unit (14), and traction means (9), e.g. a rope or a drive belt, wound around the pulley (10), the component (7) to be moved being either attached to the traction means (9) or connected with the drive unit (12). In order to provide a drive unit (12) enabling collision detection, emergency stop functionality, and improved handling with regard to control of the motion of the component (7) by an operator of the X-ray device (1), the invention proposes that the motor and gear unit (14) is rotatable about the axis of the drive shaft (13) against the elastic force of a balancing spring (15), wherein provision is made for a rotation sensor (17,24), which rotation sensor (17,24) is adapted for detecting a rotation of the motor and gear unit (14) and for generating a corresponding rotation detection signal.