Background: Cystic fibrosis (CF) is an inherited autosomal recessive disorder that causes chronic airway disease. In addition to genetic factors, environmental factors may affects the clinical phenotype of CF. In our study, the presence of aeroallergen sensitivity in our patients with CF and its effects on clinical findings were evaluated. Materials and Methods: Demographic characteristics, clinical and laboratory findings, skin prick test (SPT) results, and Modified Shwachman-Kulczycki (MSK) scores of patients diagnosed with CF followed in the Pediatric Respiratory and Allergy Clinic of Dokuz Eylul University Faculty of Medicine were evaluated. Results: We evaluated 51 patients with CF with a median age of 10 (6-18) years. The mean MSK score of the patients was 72.54±11.50, and the mean predictive value of forced expiratory volume (FEV1) in the first second of 41 patients was 80.43±19.50. According to SPT, aeroallergen sensitivity was detected in 17 (33.3%). The frequency of bacterial colonization and bronchiectasis was higher, MSK scores were lower in AF-sensitive patients (p≤0.01). However, there was no similar difference in other allergen sensitivities. MSK scores and predictive FEV1 values of 25 (49%) patients with bacterial colonization were significantly lower than those without colonization (p=0.001, p=0.005, respectively). Conclusion: Aeroallergen sensitivity was detected in approximately 1/3 of CF patients. Although it has been emphasized in studies that environmental factors may have an impact on lung functions and clinical conditions in CF, the effect of allergens other than AF sensitivity may be less important compared to other environmental factors such as the presence of bacterial colonization. Keywords: Cystic fibrosis, atopy, children, asthma, Aspergillus fumigatus, Pseudomonas aeruginosa