The invention relates to an X-ray detector with detector elements (1) arranged in a layer. The detector elements (1) contain a scintillator element (2) for the conversion of X-rays (X) into photons (v), a photodiode (5) for detection of the photons (v), and a processing circuit (4) for the processing of electric signals generated by the photodiode (5). In order to protect the electronics (4) from X-rays a shielding (3) of variable effective thickness (d1, d2) is disposed in front of the electronics (4). This shielding (3) can in particular be L-shaped. By reduction of the effective thickness of the shielding (3) to a necessary minimum the volume of the scintillator unit (2) can be maximized.