Objective: to evaluate tolerability of different chemotherapy regimens in children with pulmonary TB and input of second-line drugs to the development of adverse drug reactions (ADR). Materials and methods. The study enrolled 92 children aged 2–12 years (a median of 6 years of age) with newly diagnosed active pulmonary TB, who received treatment in 2019–2022. The initial drug combination was based on drug susceptibility of both infection source and patient (chemotherapy regimens 1/3, 2 and 4/5); the number of TB drugs and chemotherapy duration was determined by severity of TB process. The patients were divided into groups based on the chemotherapy regimen: group 1 included 29 patients only administered first-line drugs (1/3), 16 patients of group 2 received chemotherapy regimen 2, and 47 patients of group 3 received 4/5 chemotherapy regimen. Results. ADR were observed in 61 of 92 children (66,3%); satisfactory tolerability was observed in 31 children (33.7%). ADR occurred most frequently in patients of group 3 (85.1%) compared to group 2 (68.8%) and group 1 (34.5%) (χ2 = 20.624, p < 0.001). ADR, which required withdrawal of the offending drug, were more frequent among children, who received chemotherapy regimen 4/5 or 2 (55.3% and 50.0% respectively) compared to children, who received chemotherapy regimen 1/3 (10.3%) (χ2 = 15,372, p = 0,001). Allergic reactions were reliably more frequent under chemotherapy regimen 4/5 compared to chemotherapy regimen 1/3 (31.9% and 6.9% respectively) (χ2 = 6,464, p < 0,012). Clinical and laboratory manifestations of allergic reactions were identical and did not depend on the chemotherapy regimen. Toxic reactions were reliably more frequent under chemotherapy regimen 4/5 compared to 1/3 (48.9% and 20.8% respectively) (χ2 = 6.064, p = 0.014). The range of toxic reactions increased under administration of second-line drugs and demonstrated more clinical and laboratory manifestations under chemotherapy regimen 4/5. Intractable ADR most frequently occurred under administration of amikacin/capreomycin (41.7%), protionamide (30.0%), levofloxacin/moxifloxacin (17.0%), or cycloserine (11.6%). Conclusion. The frequency of ADR to TB treatment in children depends on the administered drugs. The least incidence of adverse reactions was observed in patients, who received first ling drugs (chemotherapy regimen 1/3). Toxic reactions prevailed over allergic ones. The range of toxic reactions increased in patients, who received second-line drugs.