Aneurysmal bone cyst is rarely found in the mandible, and roentgenographic diagnosis of this condition is not easily made. In this report, the diagnostic value of bone scintigraphy and radionuclide angiography and CT imaging in two cases of aneurysmal bone cyst of the mandible are discussed. Bone scintigraphy with Tc-99m MDP demonstrated ring-like or doughnut-pattern accumulation of radioactivity, which corresponded to the expansile character of the bony lesion. The accumulation of radioactivity was intensive in the peripheral region despite the fact that the lesion was benign. Furthermore, the central rarefaction showed that the lesion was cystic. Radionuclide angiography with Tc-99m HSA, including blood pool scan, did not detect radioactive concentration. Thus bone scintigraphy and radionuclide angiography were found to be essential in the differential diagnosis of aneurysmal bone cyst from other forms of tumor, especially hypervascularized tumor and central hemangioma of the mandible.