The objective: selection of optimal timing for chest CT to identify respiratory tuberculosis treatment failures in children and adolescents through clinical and radiological comparison.Subjects and Methods. A retrospective comparative study was conducted. Totally 70 patients aged from 2 to 17 years with various clinical forms of respiratory tuberculosis were examined. Retrospectively, patients were divided into 3 groups: Group 1 (35 people) – CT was performed before the treatment start and, as the first control, after 2-3 months of chemotherapy; Group 2 (17 people) had a CT before the chemotherapy start and after 2-3 months – plain X-ray (or in combination with linear tomography), CT control – after 6-9 months after the chemotherapy start; Group 3 (18 people) included patients who had only plain X-ray (or in combination with linear tomography) before and during chemotherapy, CT was first performed after treatment failureResults. In all groups, in more than 40% of cases, radiological changes were the only informative criterion of treatment failure. CT performed in the early stages was optimal for timely detection of treatment failure: before the chemotherapy start and in 2-3 months (Group 1). In patients of Groups 2 and 3, opportunities for timely correction of chemotherapy were missed due to inadequate assessment of pathological changes. CT performed after 6-9 months of treatment reliably revealed irreversible changes in 53% and 78% (Groups 2 and 3), respectively.