OBJECTIVE: To evaluate the usefulness of submitting children with thyroid cancer secondary to nuclear accidents to a completion total thyroidectomy. DESIGN: A case series consisting of patients living and operated on in Belarus whose parents had asked for a clinical evaluation in a western European center. SETTING: A tertiary care referral center. PATIENTS: The conditions of 47 children from Gomel, Belarus, with differentiated thyroid carcinoma following the nuclear accident at Chernobyl, Ukraine, were evaluated at the University of Pisa, Pisa, Italy. In approximately half of the cases, the treatment in Belarus consisted of a hemithyroidectomy. After a complete evaluation, the decision was made to reoperate on 19 of them by performing a completion total thyroidectomy. The preoperative evaluation revealed that 5 (26%) of the 19 patients who had undergone a hemithyroidectomy had unilateral recurrent nerve palsy and that 2 (10.5%) had hypoparathyroidism. INTERVENTIONS: Neck ultrasonography was used for the preoperative localization of thyroid residuals, thyroid nodules, suspicious lymph nodes, and a guided fine-needle aspiration biopsy specimen. The circulating thyroglobulin measurement was obtained before reoperation. An iodine 131 whole-body scan (WBS) was performed and circulating thyroglobulin levels were obtained after completion of the thyroidectomy during withdrawal of levothyroxine sodium therapy. MAIN OUTCOME MEASURE: The number of patients with a recurrence of thyroid cancer and lung or lymph node metastases after the completion total thyroidectomy. RESULTS: The results of the histologic examination were positive for papillary thyroid cancer in 6 (28.6%) of 21 patients, 3 with residual cancer in the remaining thyroid lobe and 3 with metastatic lymph node disease. A posttherapy WBS demonstrated lung metastases in 5 (28%) of 18 patients and lymph node metastases in 6 (33%) of 18 patients; the results of a posttherapy WBS were negative for metastases in 7 (39%) of 18 patients. Hypoparathyroidism developed in 4 (21%) of 19 patients who underwent a completion total thyroidectomy; unilateral laryngeal nerve palsy developed in 1 (5.2%) of these 19 patients. Among 22 children who previously underwent total thyroidectomy in Belarus, a diagnostic WBS showed lung metastases in 10 (45%) of the children and lymph node metastases alone in 3 (14%) of the children; the results of a diagnostic WBS were negative for metastases in 9 (41%) of the children. Statistical analysis showed a nonsignificant (P>.05) difference in the prevalence of lung and lymph node metastases in patients who previously underwent total thyroidectomy compared with patients who underwent completion total thyroidectomy. CONCLUSION: Completion total thyroidectomy allowed for the diagnosis and treatment of recurrent thyroid cancer and lung or lymph node metastases in 61% (11/18) of the patients in whom residual differentiated thyroid carcinoma was not previously recognized.