The problem of thyroid cancer in Russia became especially relevant after the accident at the Chernobyl nuclear power plant in 1986. We can trace the dynamics of morbidity in the population of Leningrad-Saint Petersburg from 1980 to 2018. for the periods before and after the accident, even before the inclusion of this localization of malignant neoplasms in the state reports. Thyroid cancer can be attributed to rare malignancies. In addition to morbidity and mortality, it is planned to consider such analytical indicators that are practically not used in Russia as the reliability of accounting, partial mortality and five-year survival of patients with thyroid cancer calculated according to the international standard. In many territories of Russia and abroad, an increase in the incidence of thyroid cancer has been detected, which to some extent may be associated with its overdiagnosis, against the background of a decrease in the population’s mortality from this cause. Favorable patterns were found in relation to the reliability of accounting in Russia and especially in Saint Petersburg. Some structural changes were detected in the histological structure of thyroid cancer.