An image storage and display system transmits required image data such as original image data and irreversible compressed image data expediently. Original image data input to the image server from the input modality is subjected to a data compression process by the server computer ad irreversible compressed image data having a decompression ratio of 1/20, 1/50, etc. is thereby produced. In this way, three versions of image data, original image data, and two irreversible compressed image data having different compression ratios are created for a single image and stored in a temporary storage medium. A request is issued from a workstation, connected to the image server via a network, for transmission of the version of image data to be acquired, and the requested image data is read out from the temporary storage medium, transmitted to the workstation and displayed on a monitor.