Respiratory infection in cystic fibrosis develops in the first years of life and plays a key role in shaping the prognosis of the disease. Microbiology of respiratory infection in such patients is significantly different from that in patients without cystic fibrosis. Adequate antibiotic therapy with inhaled drugs can delay and sometimes even prevent the onset of chronic Pseudomonas aeruginosa infection, while significantly extending the years of qualitative life of patients with cystic fibrosis.