Introduction. COVID-19 is a highly contagious infectious disease caused by the novel coronavirus SARS-CoV-2. After the acute phase and discharge from the hospital, convalescent people continue to have respiratory symptoms, changes in pulmonary function (PF) and indicators of chest computed tomography (CT).Aim. To evaluate changes in PF and quantitative CT data in patients after severe coronavirus pneumonia.Materials and methods. A cross-sectional observational study was conducted: 55 patients (including 28 men, aged 32–78 years) with a diagnosis of “lung interstitial process due to a coronavirus infection” were examined. All patients underwent a study of PF (spirometry, body plethysmography, measurement of the diffusion lung capacity: DL_CO) in the interval of 24–305 days after discharge from the hospital. CT scan of the chest was performed simultaneously with the functional examination (±30 days), the parameters were calculated: ground glass areas, functional lung tissue volume (FV), affected tissue volume (AV), CovidQ (AV/FV ratio).Results. A decrease in DL_CO was found in 28 patients. Restrictive disorders – in 13 patients, obstructive disorders – in 2 patients. At the time of the CT examination, all patients had residual changes in both lungs of varying severity. Functional parameters (FVC, TLC and DL_CO) were statistically significantly correlated with the CT data.Conclusion. During the recovery period in patients after COVID-19, lung structural changes, according to CT scans, persist for at least 3 months. Pulmonary ventilation indicators in most patients normalize during this time, half of the patients retained a decrease in diffusion lung capacity. Acknowledgment. The study was carried out as part of the state task on the topic: “The impact of the new coronavirus infection SARS-CoV-2 on the functional parameters of the respiratory system during the convalescence period” (code: “PostCOVID-functional diagnostics”).