A mobile X-ray detector system is disclosed including a mobile X-ray detector and a mobile dosimeter arranged on the X-ray detector, at least during operation. Furthermore, an X-ray facility is disclosed for cooperating with such an X-ray detector system, an X-ray system including such an X-ray facility, and a corresponding X-ray detector system, as well as a mobile dosimeter and a mobile X-ray detector for constructing such an X-ray detector system.