An image processing apparatus defines at least two display regions on a designated and displays a target three-dimensional medical image in one of the display regions based on three-dimensional volume data. When specifying the coordinates of an input point designated in the display region, the image processing apparatus records at least the specified coordinates as history information. The image processing apparatus further specifies a continuous region containing the specified coordinates. When the continuous region is specified, the image processing apparatus displays an image showing a region of interest in one of the display regions by displaying at least one image showing the specified continuous region in a display region different from the display region where the target image is displayed.