In a method and x-ray system for determination of the relative position of an x-ray source relative to an x-ray image detector, a reference structure in a known position relative to the x-ray source is introduced into the beam path between the x-ray source and the x-ray image detector. The x-ray image detector acquires an x-ray image with the map of the reference structure. The position of the map of the reference structure in the x-ray image is determined by a computer and the position of the reference structure relative to the x-ray image detector is determined therefrom. The position of the x-ray source relative to the x-ray image detector is determined from this relative position of the reference structure to the x-ray image detector and from the position of the reference structure to the x-ray source.