BACKGROUND: The potential association between the lung function status at baseline and TB treatment outcome has not been evaluated previously. We aimed to investigate the impact of lung function status at the time of TB diagnosis on treatment outcome in patients with pulmonary TB (PTB).METHODS: A retrospective cohort study on data from all consecutive patients with culture-confirmed PTB and available spirometry test results admitted during the year 2016 to the Regional anti-TB dispensary no.1 in Kharkiv, Ukraine.RESULTS: A total of 278 patients with PTB were included into the study. The rate of negative treatment outcome (failure or death) was higher in patients with restrictive and mixed lung dysfunction than in those with normal spirometry results (25.6% vs. 6.8%, P = 0.0007; 37.5% vs. 6.8%, P = 0.003, respectively). In a logistic regression model, restrictive lung disease and mixed-type lung disease were associated with negative treatment outcome (OR 4.19, 95% CI 1.60-13.28, P = 0.007 and OR 5.46, 95% CI 1.28-24.44, P = 0.02, respectively).CONCLUSIONS: Lung function at the time of diagnosis has an important impact on treatment outcomes in patients with PTB; the more severe the restriction in lung function the higher the likelihood of a negative treatment outcome.