To assess the ability of CT to demonstrate the different types of emphysema, the CT appearance was compared with the corresponding barium-impregnated pathologic specimens cut in the transverse plane, in four patlents with emphysema. The CT appearance was also compared with the chest radiographs of two patients with irregular emphysema associated with progressive massive fibrosis. The parenchymal destruction visualized on CT in the patients with mild and moderate centriacinar emphysema was distinctly different from that seen in the patient with panacinar emphysema in appearance and distribution. Paraseptal and irregular emphysema were also well demonstrated using CT. Window widths between 800 and 1,500 were found to demonstrate the parenchymal changes most accurately. We conclude that CT can help to identify the presence of emphysema and to distinguish radiologic characteristlcs of the different types of emphysema.