An apparatus for bone densitometry (1) includes a patient-carrier frame (2) fitted with a support surface (21) for a patient and an arm (3) movable with respect to the frame (2) in a longitudinal direction (X) from the feet to the head of the patient. The arm is fitted with a generator-detector assembly having an X-ray generator (31) and an X-ray detector (32), mechanically aligned so that the collimated beam (F) of X-rays produced by the generator (31) centers the detector (32). In particular, the frame is a monocoque (2) and fully supports, at the support surface (21), the arm (3) in order to leave the space underneath the frame (2) free. Advantageously, moreover, in the case of apparatus with frame (2) made of aluminum, the frame itself also serves as a filter for X-rays.
