Preoperative evaluation of the mandible for invasion by tumor has always been a difficult problem. Various radiologic methods have been used, but from clinical point of view they have not been satisfactory. We compared the diagnostic efficacy of panorex, bone scan, CT scan in 21 patients with squamous cell tunor of the oral cavity and tonsils which were close or adherent to the mandible. Our data shows bone scan has low efficacy and many false positive results. False negative were similar among these methods. CT scan of the oral cavity tumor with needs bone window setting is suggested for the evaluation of the mandible preoperatively.