The invention relates to an X-ray CT scanner and a diagnostic imaging apparatus. In an embodiment of the X-ray CT scanner (1), an X-ray tube (12a) emits rays. A detection unit (13) detects X-rays that have been emitted by the X-ray tube (12a), and have passed through a subject. A data collection unit (14) collects projection data on the basis of detection data detected by the detection unit (13). A reconstruction unit (35) generates a reconstructed image on the basis of the projection data. A display unit (32) displays a display image based on the reconstructed image. A receiving unit (31) rotates a first display image, which is based on a first reconstructed image generated by the reconstruction unit (35), on a display screen of the display unit (32), and receives an operation specifying a prescribed region in a second display image that establishes a direction different from a slice direction as an axis. The reconstruction unit (35) generates a second reconstructed image of the prescribed region on the basis of the projection data, so as to have a higher resolution than that of the first display image.