Treatment of patients with non-small-cell lung cancer (NSCLC) is one of important problems of current oncology practice. The first-line NSCLC chemotherapy standards are based on the platinum-containing medications. Today, immunotherapy is considered to be the best option for the second-line NSCLC treatment after the platinum-based chemotherapy. In the Russian Federation, nivolumab and pembrolizumab are recommended to be used in such clinical situations. The aim of the study was to estimate the costs of the immunotherapy when used for the second line NSCLC treatment. Materials and methods . Direct comparative studies between nivolumab and pembolizumab have not been conducted, but in previously published studies, no statistically significant difference in efficacy between nivolumab and pembolizumab in second-line therapy of NSCLC was identified. With regards to this, the analysis from the stand point of the healthcare system, the research was carried out by using the method of cost minimization with the Markov model. The data on pricing entered with no discounts for a period of 1-5 years. The costs of the immunotherapeutic drugs were taken from the results of auctions current year. In the basic version, the calculations were made for a patient with a body weight of 70 kg. It was assumed that nivolumab is given at a dose of 3 mg/kg every 2 weeks, and pembrolizumab – at a dose of 2 mg/kg every 3 weeks. Only the costs of the immunotherapeutic drugs and the expenses for their administration were taken into account. In the sensitivity analysis, the impact of cost changes within reasonable limits, on the total expenses were analyzed for patients of 60-80 kg body weight. Results . The costs of the immunotherapy during the first year of treatment are maximal and amount to 84% of the total expenses. At the same time, the cost of pembrolizumab for 5 years of treatment (in the basic version) is 5.7% lower than that for nivolumab. When prices vary within reasonable limits, the use of each of these two drugs may become economically justified. If the patient body weight ranges from 67 to 80 kg, the use of pembrolizumab is economically more beneficial. Conclusions . As nivolumab and pembrolyzumab used for the second line therapy of NSCLC in this study are similar in terms of the treatment costs. Depending on the price variations within reasonable limits and the patient body weight changes, each of these drugs can be economically preferable.