The invention relates to a method for the surface scanning of a patient, arranged on a patient's couch of a medical diagnostic device, with the following steps: Radiation of a light beam from a positioning light source onto the patient, detection of the light beam on the patient by an image sensor, arranged offset relative to the light beam, with the said light beam running from the positioning light source to the patient, movement of the patient relative to the positioning light source so that the light beam passes over the body of the patient, and determination of the surface of the patient from the detected light beam. A corresponding device is also claimed.