PURPOSE: To determine the correlation between areas of decreased parenchymal attenuation seen in cases of bronchiectasis, and the severity and extent of the condition, as revealed by HRCT and the plmonary function test (PFT). MATERIALS AND METHODS: The findings of forty-five patients with bronchiectasis who had undergone PFT and HRCT were retrospectively analysed. CT scores were calculated according to the severity and extent of the condition, and areas of low attenuation, and the correlation coefficients between these were determined. Bronchiectasis was classified as either cylindrical or cystic, and using Student's t test, the statistical significance of the results of the PFT were determined. RESULT: The severity and extent of bronchiectasis correlated with the extent of areas of low attenuation (r > .45, p < .05), with especially significant correlation between the extent of these areas and the extent of the condition (r =.84, p=.0001). Correlation was greater in cases involving the cylinlrical variety than the cystic. The extent of low attenuation areas correlated with FEV1, FVC, MMEF, and DLCO (r > .44, p < .01). The functional parameters of the PFT which help differentiate between cylindrical and cystic bronchiectasis are FEV1, FVC, MMEF, DLCO (p < .01), RV, and TLC (p < .05). CONCLUSION: In patients with bronchiectasis, the extent of the condition correlated closely with the extent of low attenuation, and the latter, especially in cases of cylindrical bronchiectasis, showed significant correlation with the extent of abnormalities revealed by the pulmonary function test.