Actuality: Ps. aeruginosa infection in patients with cystic fibrosis (CF) leads to severe evolutions accompanied by serious impairment of the lung function. Aim: The assessment of spirometric indices in patients with CF associated with Ps. aeruginosa bronchial colonisation. Methods: The study presents the data of 32 patients with CF (age 5-25 years), 25 of them with Ps. aeruginosa infection and 7 without this germ colonisation. Respiratory functional exploration in patients with CF was run out through spirometric examinations during pulmonary exacerbations. Results: Spirometry examinations emphasize the restrictive disorders in all patients with CF (FVC 61,96±0,59%). Ps. aeruginosa infection determines a significant diminishing (p<0,01) of FVC-58,96±0,48% in comparison with Ps. aeruginosa non-infected patient values (72,71±1,15%). Broncho-obstructive syndrome in patients with Ps. aeruginosa is characterized by a pronounced reduction of FEV1 (54,44±0,52%; p<0,01) and PEF values (49,56±0,49%; p<0,01) compared with the same indices in the group of the patients without Ps. aeruginosa infection (FEV1 77,57±1,2%; PEF 65,42±1,3%). The severity of the obstructive disorders, caused by the chronic pulmonary inflammation with Ps. aeruginosa is confirmed by a veraciously reduction of FEV25-75 (47,24±0,78%, p<0,01), that in the cases of CF without Ps. aeruginosa colonisation were less affected (79±1,68%). Conclusion: Pulmonary infection with such aggressive germs as Ps. aeruginosa, represents a determinant factor for the progressive evolution of CF and assumes a significant diminishing of suggestive spirometric indices for restrictive and obstructive pulmonary disorders.