PURPOSE: To evaluate the relationship between type, extent, and associated decreased attenuation areas ofbronchiectasis, as seen on high-resolution CT (HRCT), and abnormalities on pulmonary function tests. MATERIALS AND METHODS: We retrospectively evaluated 34 patients with bronchiectasis, in whom inspiratory and expiratory HRCTscans and pulmonary function tests were performed. HRCT scans were reviewed for the type (cylindrical vs. cystic)and extent of bronchiectasis (number of segments), and the extent of decreased attenuation areas seen oninspiratory (number of segments and CT scores) and expiratory scans (CT scores). With regard to the type andextent of bronchiectasis and the extent of decreased attenuation areas, as seen on HRCT, three radiologistsreached a consensus. We evaluated the relationship between pulmonary function tests (FEV1, FVC, FEV1/FVC, MMEF)and HRCT findings using Pearson correlation coefficients and linear regression (PC-SAS). RESULTS: In all patientswith bronchiectasis there were areas of decreased attenuation, as seen on inspiratory and expiratory HRCT. Theextent of bronchiectasis showed strong positive correlation with the extent of decreased attenuation seen oninspiratory and expiratory HRCT (p < 0.001). On pulmonary function tests, the extent of bronchiectasis anddecreased attenuation correlated negatively with FEV1, FVC, FEV1/FVC and MMEF. Cystic bronchiectasis tended to bemore extensive than the cylindrical variety (12.2 vs 7.6 ; CT score:34.7 vs 15.6) and expiratory scans (CT score :38.1 vs 19.1) CONCLUSION: There is significant correlation between the extent of morphologic abnormality, as seenon HRCT, and the physiologic impairment of pulmonary function tests in patients with bronchiectasis and associateddecreased attenuation areas.