Objective: to study the balance of TB patients admitted to prisons, including TB patients identified during the initial examination in pre-trial detention centers, and active TB patients released from prisons in Russia. Materials and methods. We analyzed the official statistics of the Federal Penitentiary Service on the number of new cases of tuberculosis in pre-trial detention centers, the number of TB patients who arrived in pre-trial detention centers and left prisons for 2014-2021, the number of cases detected during the initial examination in pre-trial detention centers and during their stay in them from 62 regions of Russia in 2021. Results. The balance of tuberculosis patients who arrived in prisons and left them consists of previously known tuberculosis patients who arrived in pre-trial detention centers (known from statistical data), tuberculosis patients identified in pre-trial detention centers during the initial examination (unknown) and active tuberculosis patients released from prisons (known from statistics). Since we do not know the number of TB patients identified in pre-trial detention centers during the initial examination and who fell ill during their stay in pre-trial detention centers, but we know the number of TB patients first detected in pre-trial detention centers, we used two modeling approaches. The first approach included determining the expected number of cases during their stay in pre-trial detention centers from the moment they were placed in them until they were released or transferred to correctional institutions, based on data on the annual incidence of tuberculosis in correctional institutions and the number of years spent in pre-trial detention; this approach gave the maximum ratio of the number of patients who fell ill during the stay in the pre-trial detention center to the number of patients identified during the initial examination. The second approach was based on determining the proportion of patients identified in the pre-trial detention center on the basis of a selective study. It was found that in 2021 the balance between arrivals (including those identified during the initial examination) and departed patients ranged from -378 to -624 people. In previous years, the balance was also negative. Thus, fewer patients enter prisons than leave them. Conclusion. According to mathematical modeling, the Russian penitentiary system is a "filter" that allows to identify and treat cases of tuberculosis among the socially vulnerable population. When planning national TB programs, it is necessary to allocate funds to improve the effectiveness of the treatment of TB patients in prisons.