A 65 years old female patient suffering from multinodular goitre and from hypercalcaemic syndrome which had been and was being treated with drugs for a number of years. The patient undergoes total thyroidectomy. Surgical neck and anterior mediastinum exploration was negative for sick parathyroids. Neck and chest TC and `TC sestamibi scintigraphy showed the presence of a 7 cm hyperfunctional ectopic parathyroid tissue in the postero-superior mediastinum infiltrating oesophagus.Video bronchoscopy revealed an extrinsic compression of the trachea. The patient underwent surgery. Through right posterolaterai thoracotomy and mediastinal pleura incision, the adenoma excision was carried out. The histological examination revealed a potentially malignant parathyroid adenoma with infiltration, without overreaching the capsule. The surgical treatment resulted in an immediate resolution of the clinical simptomatology. One year later, the follow up bas shown no observable relapse with normai calcium and PTH values. Today, the tendence to minimally invasive surgery, an accurate preoperative localization of the adenoma and the use of techniques such as intrasurgical nuclear mapping through manual gamma probes, selective angiography, venous intraoperative dosage of PTH and intrasurgical ultrasound scan.