In a method and device for generating a tomosynthetic 3D x-ray image, a number of digital x-ray images of an examination subject are acquired at respectively different projection angles, within a limited angle range, using an x-ray source and a digital x-ray detector. At an initial position for a selected projection angle, a spatially-fixed reference point is projected onto a partial region of the acquisition surface of the x-ray detector. For each further projection angle, a corresponding partial region on the acquisition surface is automatically determined. The tomosynthetic 3D image is reconstruction exclusively using image data from the respective partial regions.