The results of treatment of 330 children (< 14 years) and adolescents (15-18 years) with thyroid cancer who were operated on at the Institute of Endocrinology after the Chernobyl accident in 1986 were analyzed. The number of young patients increased after 1986 (1981-1985, 9 cases; 1986-1990, 37 cases; 1991-1995, 177 cases; 1996-1998, 116 cases). Most of these children and adolescents were younger than 8 years at the time of the accident (84.2%). More than half of the children (58.1%) lived in areas receiving the highest radiation exposure. These thyroid cancers developed after a short latent period, were more aggressive at presentation, and expressed regional (57.3%) or distant (14.5%) metastasis. Solid papillary cancers were present in 93.1%. Coexisting thyroid conditions were common (thyroid hyperplasia, 25.1%; nodular goiter, 18.8%; chronic thyroiditis, 10.2%). Most patients were treated by total thyroidectomy with intraoperative visualization of recurrent laryngeal nerves and parathyroid glands. When lymph node metastases were identified, a modified neck dissection was performed. Such operations were done in 277 (84.1%) patients. Postoperatively, the patients were treated with radioiodine and thyroid-stimulating hormone suppressive therapy. Postoperative complications included recurrent nerve palsy in 12.3% and permanent hypoparathyroidism in 6%. Operations for local recurrence of cancer were performed in 2.8% cases and for regional metastasis in 4%. The general mortality was 1. 8%. We anticipate that there will be more patients with thyroid cancer during the next few years. Therefore this high risk population for thyroid cancer must be carefully monitored and evaluated during the next several decades.