The purpose of this study is to evaluate the usefulness of multidetector helical CT (MDCT) with three-dimensional (3D) postprocessing for assessing the lung volume at inspiration and expiration of the pulmonary emphysema and for comparing it with pulmonary function tests. Percentage lung volume at the threshold of -930, -900, -810, -790, and -770 at expiration showed good correlation with FEV1, FEV1/FVC, and DLCO/Va. Excellent correlation was observed between percentage lung volume at the threshold of -900 and FEV1/FVC. CT densitometry at expiration showed better correlation than that at inspiration with pulmonary function tests. MDCT with 3D technique is useful for assessing the severity of pulmonary emphysema.