BACKGROUND Thyroid cancer in children and adolescents has rarely been reported in Taiwan. The purpose of this study is to realize the characteristics of thyroid cancer of children and adolescents. METHODS From 1971 to 1992, a total of 726 patients with cancer of thyroid were treated at Veterans General Hospital-Taipei. Of these, 37 were below the age of 21, and were followed 1 to 21 years with an average of 7.4 years. RESULTS Only one patient with thyroid cancer had the history of previous radiation therapy for head and neck tumor. Neck mass was the most common mode of presentation and 36% had associated cervical adenopathy. Histologically, papillary cancer was found in 29 patients, follicular cancer in 7 and medullary cancer in 1. There was no undifferentiated cancer. Twenty-three patients had lymph node metastases. Eight patients developed distant metastases, especially to the lung, and most of them were male. Recurrence after initial surgical treatment was found in 12 patients, without significant association with the surgical procedure. The major operative complication was hypoparathyroidism. Disease-related mortality occurred in only one case (2.8%). CONCLUSIONS Well-differentiated carcinomas of the thyroid in children and young adults are rare in Taiwan and are mostly papillary carcinomas not related to previous neck irradiation. Before the age of puberty, boys were predominant in this series. The rate of distant metastasis was higher in males. The prognosis after surgical treatment is excellent.