The purpose of the invention is to create a mechanically uncomplicated installation for producing radiographic layer images, making it possible to use small radiation dosages and, however, to collect sufficiently information on the object by one exposure, whereby separation of the superimposed layers from each other in a desired way for visualization can be accomplished by means of tomosynthesis. The installation includes radiation generating means (1, 2), collimating means for confining the radiation and focusing it on an object (4) to be radiographed, e.g. a patient, means (10) for detecting the radiation passed through the object and means for storing and processing the information contained in said detection. Said collimating means comprise a collimation unit (3) including at least two separate, narrow, contiguous, substantially parallel collimating slots (5) for producing narrow, fan-shaped beams, said slots being arranged preferably in alignment with the longitudinal axis of the object to be radiographed. The installation also includes means (11, 13) for displacing said collimating slots and the object to be radiographed in relation to each other at least substantially in alignment with the normal of said collimating slots, those parts of the object selected to be radiographed being arranged to be exposed to radiation by said narrow fan-shaped beams from a number of different directions. The information obtained from the object to be radiographed is stored preferably in digital form and processed for visualization.