Ectopic parathyroid adenoma or hyperplasia in the mediastinum are seen in a percentage of patients with hyperparathyroidism and have generally been treated by conventional open surgery. However, due to recent improvements in the ability of diagnostic imaging such as 99mTc-methoxyisobutylisonitrile (MIBI) scintigraphy to identify these lesions, we have been obtaining favorable results from thoracoscopic excision of mediastinal parathyroid tumors. In thoracoscopic surgery, three to four trocars were inserted between the fourth and seventh ribs from a lateral approach. Based on diagnostic imaging, tumors were identified and excised by the shortest possible route. Surgery time for four consecutive patients ranged from 50 to 140 min, and hemorrhage volumes were small. No intra- or postoperative complications were observed, and the postoperative course for these patients has been uneventful. Analgesia was required only a few times for each patient. In the most recent patient, radioisotope-navigated thoracoscopic excision was performed using 99mTc-MIBI. When thoracoscopic excision was combined with radioisotope navigation, tumor identification took less time, cutting the surgery time in half and ultimately placing less stress on the patient.