Incidence of unexpected diagnosis of thyroid carcinoma among operations on benign thyroid surgical diseases (nodular goiter and Graves' disease) was studied in 608 patients within 2008-2009 years in specialized clinic of endocrine surgery. In 56 (9.2%) patients the "incidental" thyroid carcinoma including 43 (77%) - papillary microcarcinoma were diagnosed in histological investigations. In 10 (18%) patients which were performed within the first postoperative week. Repeated surgery demonstrates increased risk of complication (damage of parathyroid glands, recurrent laryngeal nerves and other anatomic structures of neck) considering less favoring conditions for secondary operations, it is worth to implement wider indications to frozen section, radical primary operation (total thyroidectomy at multi-nodular bilateral goiter and Graves' disease), and also maximal complete examination prior to surgery.