A diagnostic X-ray apparatus emitting pulsed X-ray radiation includes a processor for performing digital X-ray subtraction of a previous mask image from current images. The apparatus includes circuitry for digitization of the video signals from an image intensifier-TV chain, digital subtraction to obtain digital difference signals, and subsequent reconversion of the resultant digital difference video signals to analog signals. Pulsed X-ray exposures are performed during the blanking periods of the TV camera following which the television fields immediately following the pulsed X-ray exposure are scanned and read out, and are supplied to the processor for performing the digital X-ray subtraction.