This study aimed to determine the impact of density correction on emphysema quantification and identify the optimal site for air density correction on volumetric CT scans. CT scans of 78 COPD patients were analyzed. Density correction using tracheal and external air measurements was conducted, and emphysema index (EI) and mean lung density (MLD) were calculated. Significant differences were observed in air densities, MLD, and EI before and after density correction. Correlations between CT quantification indices and pulmonary function tests (FEV1 and FEV1/FVC) improved after density correction. Tracheal air correction yielded better results than external air correction. The study concludes that density correction improves the correlation between emphysema quantification and pulmonary function tests on volumetric CT data.