In a method and device for determination of a position shift, first image data of a body region of a treatment-positioned patient that contain derivable temperature information are acquired. A focal area in the body region is determined, and the focus of a hyperthermia applicator can be aligned on the focal area. Second image data of the body region of the treatment-positioned patient that contain derivable temperature information are acquired, and a position shift of the focal area is determined by a comparison of the second image data with the first image data.
