In a method for determining a position of a target region of a patient to be irradiated in an irradiation device, a patient is positioned on a patient positioning device having markers that are visible in magnetic resonance images. A magnetic resonance image data record is acquired showing a target area of the patient containing the target region, together with the markers. The magnetic resonance image data record is evaluated to determine location information describing the three-dimensional position of the target region relative to the markers. The patient positioning device with the unmoved patient is transported to the irradiation device. Target information describing the position of the target region in the irradiation device is determined from marker information indicating the position of the markers in the irradiation device, and the location information.
