The invention relates to a method for the determination of the position of a radiographic or radioscopic unit (16) with relation to a reference point (R.sub.ref) on producing a radiographic image of an object (10). The position of the unit (16) with relation to a reference point (R.sub.ref) is determined from the determination of the position of a test pattern (25), with relation to the unit (16), which is mechanically fixed to the object, by using the image of the test pattern with relation to the reference point (R.sub.ref). The invention further relates to a determining device for carrying out said method.