A device for slot scanning phase contrast X-ray imaging, includes an X-ray emitter (3), a plurality of X-ray gratings (4, 5, 6), a patient couch (7), and an X-ray detector (9). Position marker elements (1, 2) are arranged and configured in the beam path of the X-ray emitter (3) such that the position marker elements (1, 2) are visible in an X-ray image. In the X-ray image, a relative position of an object on the patient couch (7) in relation to an X-ray beam fan of the X-ray emitter (3) may be established from a location and a distance of the position marker elements (1, 2) from one another. The method thereof is illustrated in the same way. The device and the method are advantageous in that there is no need to perform high-cost and accurate mechanical adjustment of assemblies of equipment.