OBJECTIVE: Patients with cystic fibrosis (CF) have chronic pulmonary infections and, in many cases, chronic rhinosinusitis (CRS). In patients who have CRS without CF, the causative pathogens are well established, and empiric therapy is prescribed. In patients with CF, organisms are different, decreasing the efficacy of empiric therapy. Furthermore, obtaining accurate sinus cultures is invasive, making culture directed therapy more challenging. Some physicians use respiratory cultures to guide antibiotic selection for treatment of sinusitis. Previous studies have had varying results on the correlation between respiratory and sinus cultures so further investigation is warranted. METHODS: Bacterial growth from preoperative sputum, bronchoalveolar lavage, and oropharyngeal cultures were compared to the bacterial growth from intraoperative sinus cultures in patients with cystic fibrosis undergoing endoscopic sinus surgery. RESULTS: In the patients over eight years of age, 16 of 26 sputum cultures matched sinus cultures (p=0.4). When sputum cultures with normal flora and no growth were eliminated, 16 of 21 matched sinus cultures (p=0.02). No statistically significant associations were found for sputum cultures in patients under eight years of age. No statistically significant associations were found between oropharyngeal or bronchoalveolar lavage cultures and intraoperative sinus cultures from patients of any age. When Staphylococcus aureus was cultured from sputum in patients over eight years of age the positive and negative predictive values that S. aureus would be cultured from the sinuses were 100% and 75% respectively. The positive and negative predictive values for Pseudomonas aeruginosa were 73% and 86% respectively. CONCLUSION: In children with CF who are over eight years of age, organisms grown from sputum cultures are similar to organisms grown from sinus cultures when bacterial growth is present.