The pathogenesis of lung infections in patients with mucoviscidosis (cystic fibrosis, CF) is multifactorial. Both host- and pathogen-related factors are involved. The most important germ in terms of progression and pulmonary damage is Pseudomonas aeruginosa. However, the clinical relevance of other CF-typical pathogens has not yet been determined with certainty, and must be assessed on the basis of the clinical presentation of the individual case. To ensure optimal patient management, a CF-specific microbiological diagnostic work-up is mandatory. Since ever more patients now survive into adulthood, the problems associated with chronic infection are gaining in importance. In light of increasing multiresistance, the use of inhalation antibiotics, as well as combined antibiotic treatment, is becoming more and more determinative for the therapeutic outcome.