Objective - to make a comparative retrospective clinical and morphological analysis of cases of post-Chernobyl (technogenic) and sporadic (cryptogenic) papillary thyroid carcinoma (PTC) in children and adolescents in the Republic of Belarus. Material and methods. Nine hundred and thirty-six patients aged less than 19 years, operated on in 1990-2005, when cancer incidence in this age group was directly related to the consequences of the Chernobyl accident (technogenic carcinoma) were examined. A comparison group included their 140 peers who were born after March 1987 and treated in 2005-2010 for PTC (cryptogenic carcinoma). The Kruskal-Wallis test was used to compare quantitative variables; the Fisher, Pearson, and Fisher-Freeman-Halton tests were employed to compare categorical variables. All calculations were made using the R package version 2.15.0. The results were considered to be statistically significant at p<0.05. Results. Comparison of cases of cryptogenic carcinoma and those of technogenic carcinomas diagnosed in 1990-1995 and 1996-2001 revealed substantial differences in the clinical and morphological patterns of the disease. In both mentioned periods, the patients with technogenic PTC were younger than those with cryptogenic PTC (р<0.0001 and р=0.0014, respectively). The proportion of male patients in the technogenic carcinoma group was much higher than that in the cryptogenic carcinoma one (р=0.0006 and р=0.0031). The patients with technogenic carcinoma were also more frequently observed to have infiltrative tumor growth (p=0.0003 and p=0.0169) and lung metastastic involvement (р=0.0001 and р=0.0008). What is more, the architectonics of technogenic versus cryptogenic carcinoma more often contained a solid component (р<0.0001 and р<0.0001), marked intratumoral fibrosis (р=0.0008 and р=0.0266), mononuclear infiltration (р<0.0001 and р<0.0001), and no baseline abnormality (р<0.0001 and р<0.0001). Conclusion. In spite of its age similarity, technogenic carcinoma proved to be more clinically aggressive than cryptogenic carcinoma: the extent of organ invasion and the infiltrative growth of carcinoma were more frequently observed.