The progression of lung failure in children with cystic fibrosis (CF) is associated with chronic lung infection (Staphylococcus aureus, Pseudomonas aeruginosa, Achromobacter spp., etc.). Functional pulmonary tests (PFTs), spirometry and body plethysmography, computed tomography (CT) of the lungs and analysis of the lung microbiota are used for monitoring of lung condition of CF patients. Several studies have been devoted to assessing the correlation of structural changes in CT and pulmonary function tests (PFT), but at the moment there is not enough data on the relationship of these indicators and their differences depending on the respiratory microbiota in CF children in the Russian population. 
 Materials and methods. Data was collected for CF 8–17.9 years children patients. We retrospectively analyzed genotype, body mass index, results of PFTs and CT scan of the chest (score by the Brody scale), deep throat cultures in all patients, and the capillary blood gas — in 56 children. 
 Results. Significant correlations between functional tests and structural changes in the lungs were found. A trend towards impairment of PFTs and CT scores with age due to infectious pathogens was shown, and the most significant negative impact was exerted by the mucoid species Pseudomonas aeruginosa and, especially, Achromobacter spp. The last one was associated with the worst lung parameters in CF children. 
 Conclusion. Pirometry, body plethysmography, and CT of the lungs are necessary for a comprehensive assessment of the lung condition, and a study of the lung microbiome due to its influence on structural and function changes in patients with CF.