The invention relates to a positioning device for positioning a patient in a medical device comprising a patient receiving device for placing a patient and a robot arm having a plurality of movement axes for positioning the patient receiving device in a room. The positioning device can be placed into a manual operating mode in which a position of the patient receiving device in the room can be changed manually. The invention also relates to a method for operating the positioning device, comprising: providing a normal operating mode for positioning the patient receiving device automatically at a position predefined by a control device; providing a manual operating mode for manually changing a position of the patient receiving device; and switching from the normal operating mode into the manual operating mode if a switchover condition is present. The invention further relates to an irradiation device having the positioning device.