BACKGROUND: To correlate the emphysema score for quantification of the overall extent of emphysema in both lungs by CT with physiologic findings and 13 get more objective and simple method to assess the extent of em physema. METHOD: Thin-section CT and pulmonary function test(PFT) were performed in 17 patients with emphysema (all males, mean age, 62 years). Emphysema score was obtained as percentage of emphysematous lung area, dividing the total area of the emphysema(voxels with attenuation value less than -880, -900, -920HU, respectively) by the overall area of both lungs(voxels with attenuation value less than -400HU) with highlighting voxels using "Density mask" program. Emphysema score was calculated from whole lung(ESW) sod 5 representative scans(ESR) using "Density mask". Visual emphysema score(ESV) was obtained by visual assessment from 5 representative scans. Correlation of these emphysema scores(ESW, ESR, ESV) and physiologic findings were performed, comparing the ESW with ESR and ESV. RESULTS: ESW had correlation with DLCO(r=0.53-0.64) and FEVl/FVC(r=0.42-0.57) among PFT parameters. ESR had good correlation with ESW and with PFT parameters as well. ESV did not correlate with PFT parameters except DLCO. CONCLUSION: CT quantification of emphysema using "density mask" correlated well with physiologic findings. To assess the severity of emphysema, both ESW and ESR are more reliable than ESV, and ESR is recommended in routine practice as it is objective, simple and reliable.