To assess the accuracy of computed tomography (CT) in the diagnosis of emphysema, we performed CT on 32 patients prior to surgery for removal of suspected tumors. The CT scans were assessed visually for emphysema by 2 independent radiologists and 1 chest physician. Intraobserver and interobserver variation were assessed. Pathologic emphysema was graded on the resected lung specimens. These grades were correlated with the CT scores and with pulmonary function tests obtained prior to surgery. Significant correlation was found between the pathologic grade on resected lung specimens and the preoperative CT score of both the resected lobe (r greater than or equal to 0.57, p less than 0.001) and the whole lung (r greater than or equal to 0.63, p less than 0.001). Compared with pulmonary function tests, CT was a better predictor of emphysema and distinguished patients with moderate emphysema from patients with normal lungs. We conclude that CT is a useful adjunct in assessing the presence and severity of emphysema.