CT scans of 21 pateitns (intrathoracic goiter=7, Castleman disease=6, pulmonary carcinoid tumor=3, parathyroid adenoma=1, thyroid carcinoma=1, paraganglioma=1, benign pleural mesothelioma=1, sclerosing hemangioma=1) with mediastinal tumors that are known to be enhanced with intraveonus injection of contrast media, were studied retrospectively to investigate the enhancing capabilities of those tumors and to describe their CT findings. The degree of enhancement was estimated by visual inspection with a grading system. All but one case of cystic parathyroid adenoma showed enhancement on post-contrast scan, The degree of enhancement was not helpful in differentiating these tumors. Chraacteristic location and pattern of tumor extension were found in cases of intrathoracic goiter, parathyroid adenoma. thyroid carcinoma and paraganglioma. Calcifications were found in intrathoracic goiter(5/7) Castleman disease(2/6), pulmonary carcinoid (1/3) thyroid carcinoma. Necrotic low-attenuatio areas were in intrathoracic goiter(7/7) parathroid adenoma, thyroid carcinoma. Necrotic low-attenuation areas were in intrathoracic goiter(7/7). parathyroid adenoma. thyroid carcinoma and paraganglioma. In conclusion, Mediastinal tumors that are known to be enhanced in the literature were enhanced with rare exception, and if we consider the predilection site of those tumors. the scope of differential diagnosis can reasonably be narrowed.