OBJECTIVE It was the aim of this paper to report clinical and pathologic characteristics and outcome of treatment in terms of relapse-free and overall survival in 36 patients under 20 years of age and treated for thyroid cancer at Padua University Hospital from January 1968 to December 1988 and followed until December 1992. METHODS The median follow-up was 112 months (range 3 to 228 months). Age at diagnosis ranged from 4 to 20 years with a mean age of 15 years and a male/female ratio of 1:2.9. A thyroid nodule or a laterocervical mass was the most frequent sign of presentation. The routine diagnosis schedule included thyroid scintigram, neck echotomography and in the last decade fine needle aspiration biopsy. RESULTS Sixteen (28%) patients had a family history of thyroid disease. Histology revealed that papillary carcinoma was present in 43 patients (76.8%), follicular carcinoma in 9 (16%), medullary carcinoma in 2 (3.6%) and lymphoma in 2 (3.6%). Fifty-four patients were treated with total thyroidectomy, of these 34 had bilateral neck dissection and 20 unilateral nodal dissection; 2 patients underwent simple lobectomy with unilateral dissection. Nodal involvement was present in 41 (73%) cases, and synchronous visceral metastases were detected with scan and/or chest X-ray in 10 (18%) cases. In the case of differentiated thyroid carcinoma, patients with residual disease or thyroid remnants were treated with 131I metabolic therapy. All patients were put on suppressive hormone therapy. At this writing, 52 (93%) patients were in complete remission and 4 (7%) had persistent disease. Recurrences developed in 2 (3.5%) patients: one presented lung metachronus metastases and one local recurrence; no deaths have occurred. CONCLUSIONS From this experience, total thyroidectomy appears to be the appropriate approach for differentiated tumors in children and adolescents because the disease is often diffuse, secondary deposits may be easily detected, and the value of thyroglobulin measurement can be improved. Following this strategy, overall recurrence risk was low and 131I therapy was curative in patients with nodal and lung metastases.