A case of non-functioning aortico-sympathetic paraganglioma originating from left posterior mediastinum in a 34-year-old man is reported. He was found to have an abnormal shadow on the chest X-ray of an asymptomatic. His blood pressure and serological examination were within normal range on admission to our hospital. At thoracotomy a bronze 5 x 5 x 5 cm mass was recognized at the costovertebral sulcus related to the 1st sympathetic trunk. Histological examination of the surgical specimen showed that it was a paraganglioma, and neurosecretary granules were found on Grimelius staining microscopic examination. In the Japanese literature, only 13 cases of intrathoracic paraganglioma or pheochromocytoma is reported. The literature was reviewed.