A small-scale diagnostic system and a display control method are provided. In the diagnostic system, while image data on a patient is displayed on a screen of a medical image control device, when image data on another patient is received from an image generating device, and the medical doctor wants to display the received image data on the another patient on the screen for examining the image and diagnosing the another patient, the displayed image on the screen can be switched to that of the image data on the another patient by a simple operation of depressing a patient selection button. This enables the medical doctor to perform image diagnosis efficiently in a small-scale facility such as a clinic.