The invention relates to a method, system and computer software product for detecting a fiducial in digital projection images, particularly for detecting a fiducial in digital X-ray images automatically, without any operations required of the user. The invention for detecting the image of a fiducial positioned in a digital projection image is characterized in that for at least part of the digital projection image pixels, there is calculated a direction of the intensity gradient; there is defined a region of the projection image, on the basis of the directions of the intensity gradients, where the direction of the intensity gradient is changed according to predetermined limits; and there is defined a matching rate for how well the model describing the image of the predetermined fiducial matches the defined region.