"Forgotten" goiter is an extremely rare disease which is defined as a mediastinal thyroid mass found after total thyroidectomy. The authors report their experience of 7 cases of residual mediastinal goiter after total thyroidectomy for substernal goiter. Six patients were female and one male with a median age of 56 years (range: 25-70 years). Four patients were asymptomatic, 2 patients showed signs of mediastinal compression, and one patient had persistent hyperthyroidism. A sternal splitting incision associated with a cervical incision was required in 3 patients while an exclusively cervical incision was sufficient in 4 patients. Histology did not show neoplasia. Postoperative outcome was uncomplicated in 6 patients and in one patient a transient recurrent laryngeal nerve paralysis occurred. In the majority of cases forgotten goiter is the consequence of the incomplete removal of a plunging goiter, although sometimes it may be attributed to a concomitant, unrecognized mediastinal goiter which is not connected to the thyroid. The residual goiter has the same clinical presentation as an ordinary intrathoracic goiter. Our experience confirms that surgical treatment of forgotten goiter is associated with only minimal morbidity although a sternal split is sometimes required. Forgotten goiter is a rare pathology which can be prevented if particular attention is paid to preoperative imaging and intraoperative management during the first operation. However surgical treatment for forgotten goiter, when performed in specialized centers, is associated with low morbidity.