Currently, there are maximum opportunities for providing specialized oncological care to children and adolescents. Until the late 1980s, the official reporting in the USSR included the registration of cancer patients in the first age group from 0 to 29 years, which included children, adolescents, and young adults. Since 1989, the registration of cancer patients has been carried out in the USSR and Russia according to the recommendations of the International Association of Cancer Registries (IACR) for each five-year age group. However, a new problem emerged - where to classify young adults? In medicine and social sciences, young adults are considered to be individuals who have entered adulthood after the teenage period. Regarding oncology, we need to take into account the specific characteristics of the disease, primarily its structure, which significantly differs among children, adolescents, and young adults. When it comes to studying the specifics of oncopathology in young adults, it was challenging prior to the establishment of a system of population-based cancer registries, considering the relatively rare registration of primary cases of diseases in this population group. The creation of the population-based cancer registry in the Northwestern Federal District of Russia in 2019, serving a population of 13.9 million people more than the combined population of Belarus, Latvia, and Estonia provides unique opportunities to address the complex issues for this age group. This registry enables us not only to thoroughly examine the specific localization structure but also to calculate survival rates according to international standards.