Abstract It is difficult to diagnose primary hyperparathyroidism because of its variable symptoms and limited understanding of doctors. We reported one case of double parathyroid adenomas and one case of ectopic mediastinal parathyroid adenoma. Serum calcium and parathyroid hormone (PTH) was screened. 99mTc sestamibi scintigraphy single photon emission computed tomography (SPECT) had been taken to find the parathyroid adenoma. Combined with ultrasonography or CT, we localized parathyroid adenomas precisely. After the operation, both patients developed hypocalcaemia, they were treated medically, and followed up.