To assess the type, severity, and regional lung distribution of cystic fibrosis (CF) lesions as shown using high-resolution CT (HRCT), comparing these findings with chest radiographs and pulmonary function tests (PFTs), we obtained HRCTs in 36 patients with CF (mean age 13), who were clinically stable. We assessed four lung regions (upper and lower, right and left) and assigned each a semiquantitative score for (a) bronchial abnormalities, (b) parenchymal abnormalities, and (c) overinflation, based on the severity and profusion of the corresponding lesions. A similar regional assessment of chest radiographs was also done using the Chrispin-Norman method. PFT results were correlated with the radiological data. On HRCT, bronchial lesions were present in 89% of the patients and in 78% of the regions; bronchiectasis was the predominant abnormality in our population, visible in 100% of the abnormal regions. Less frequent were bronchial wall thickening (48%) and mucous plugs (29%). Parenchymal abnormalities were recognizable in 58% of the patients and 31% of the regions; alveolar consolidation was more frequent (80%) than were destructive changes (36%). Overinflation was found in 81% of the patients and 85% of the regions. We found the severity and profusion of bronchial lesions and parenchymal destructive changes to be unevenly distributed among the different regions, the upper lungs being more heavily involved than the lower, particularly on the right. Alveolar consolidation and overinflation were more uniform in distribution. HRCT patient scores correlated significantly with radiographic scores (r = 0.861) and with PFTs, especially with forced expiratory volume for 1 s (FEV1; r = 0.658). HRCT can be useful in the clinical management of patients with CF, depicting the type and distribution of bronchial and parenchymal lesions, particularly when chest radiographic results are unclear. In the planning and postural drainage, special attention should be given to the apical and posterior parts of the lungs, especially on the right; these are the areas most frequently and most severely involved by the disease.