Bone scan using radioactive isotope can be more effective than conventional X-ray radiograph for finding jaw lesion because it takes an image of the physiologic change of bone. This study is designed to show how available bone scan is able to diagnose jaw lesion better than simple X-ray and CT, as well as to determine a basis of diagnosis for jaw lesion using bone scan. The 77 patients, visiting the Oral & Maxillofacial Surgery, Department of Dankook University Hospital from January 2002. to August 2005. who were diagnosed histopathologically with postoperative malignant tumor, osteomyelitis, and bone infiltrative benign disease. Preoperative X-ray, CT, bone scan were taken and were compared with histopathologic finding. Also to compare specificty of each lesion in bone scan, bone density was measured to compare. The results were as follows. 1. Among the 25 cases of oral malignant tumor of bony invasion, a positive diagnosis associated with histopathologic evaluation, 22 cases(88%) in bone scan, 14 cases(56%) in CT image, and 10 cases40%) in simple X-ray. 2. Among the 31 cases of osteomyelitis, a positive diagnosis associated with histopathologic evaluation, 30 cases(97%) in bone scan, 23 cases(74%) in CT image, and 19 cases(61%) in simple X-ray. 3. Among the 11cases of bone infiltrative benign disease, a positive diagnosis associated with histopathologic evaluation, 11 cases(100%) in bone scan, 10 cases(91%) in CT image, and 6 cases(55%) in simple X-ray. 4. Measurement of bone density in each group showed no statistical significant difference between malignant tumor and osteomyelitis as well as benign bone disease. But, a statistical significance was seen between osteomyelitis and benign bone disease. From this results, bone scan are more sensitive than simple X-ray and CT image in jaw lesion diagnosis, but specificity shows no significant difference. Therefore, it should be suggested that evaluation of bone scan must be carrying out in reference to final histopathologic diagnosis.