An ectopically placed parathyroid adenoma in the anterior mediastinum is a rare cause of persistent or recurrent primary hyperparathyroidism (PHPT) and is recognized as an important cause of failed primary neck exploration. We encountered 3 such cases amongst 70 surgically treated patients with PHPT (4.3%) over a 20-year period. In 2 cases, the offending adenoma could be removed at first exploration whereas in the 3rd case, it was successfully removed with mediastinal exploration after 2 failed neck explorations. In established cases of PHPT with equivocal preoperative localization studies or negative neck explorations, an ectopically placed parathyroid adenoma should be considered and once localized, should be surgically removed for cure.