1. A method for registering and/or re-registering image information by means of a medical navigation system, wherein: current image information, in particular a current x-ray image of a patient to be registered using the navigation system, is produced; the position of the image information detection device, in particular of the x-ray device, is established by means of the navigation system; the current image information, in particular the current x-ray image, is compared with the aid of a computer with other image information (for example, a previously taken x-ray image); in the event of a difference between the image content of the current and previous image, the new relative position of the image information detection device or x-ray device respectively is detected and stored; and the current image information produced or current x-ray image produced respectively is registered in the navigation system, based on the information on the new relative position.