PROBLEM TO BE SOLVED: To provide an abnormal shadow candidate detection system which indicates together the detection standard of CAD for a medical image to read and the detection standard of CAD for a past image, thereby to improve the diagnostic accuracy.SOLUTION: The controller of a center server 4 searches past images, which have been obtained by taking a photograph of the same site of the same patient as a medical image input from an image displaying unit 3, and the detection result information corresponding to the past images from a past image DB, decides whether an abnormal shadow candidate detecting program used to detect an abnormal shadow candidate from the searched past images is equal or not to an abnormal shadow candidate detection program used to detect the abnormal shadow candidate from the input medical images and if the programs are not decided to be equal to each other, the controller uses the abnormal shadow candidate detection program equal to the input medical images, thereby to detect the abnormal shadow candidate from the past images and transmits the detection result information of the abnormal shadow candidate about the medical image input with the detection result information together with the searched past images to the image displaying unit 3.
