A medical advertisement can include media such as newspapers, magazines, and the Internet. Currently, the Internet is responsible for most medical advertising. Our purpose is to investigate the current status of radiologic images posted on hospitals’ websites nationwide, and to evaluate the reliability of online medical advertisements using these images. I investigated the websites of all 1,450 hospitals and 290 oriental medicine clinics nationwide. Specific information on the radiologic images posted was recorded. In terms of body parts, musculoskeletal images account for 78% of the radiologic images on hospitals’ websites and 98% of the images for oriental medicine clinics. The purposes for posting radiologic images are to explain the pathophysiology of diseases or the technique of surgical treatments, and to show the effects of hospital-specialized treatments. The most commonly used modalities of radiologic images are plain radiography and MR. More than 90% of the posted images have no source; 10% have no legends; and 5% to 7% have inappropriate legends. In terms of quality, only 60% of the radiologic images on hospitals’ websites are rated as acceptable. Fifteen percent of the oriental medicine clinics posted the radiologic images without having a medical doctor on staff. Considering the results, I conclude that it is necessary to reestablish a system of pre-screening and post-evaluation for reviewing hospital websites, especially focusing on the radiologic images posted. Then we can prevent the inappropriate information from influencing or damaging public health, and set up healthy medical competition.