To determine the value of high-resolution computed tomography (HRCT) in the diagnosis of diffuse pulmonary diseases, a direct HRCT-pathologic correlative study was performed using four inflated and fixed lungs from autopsy. In normal lungs, the smallest pulmonary artery resolved by HRCT was 200 microns in diameter; the artery was accompanied by the terminal bronchiole and the first-order respiratory bronchiole. The distance from the vessel to the corresponding lobular border ranged from 3 to 5 mm. These results suggest that the centrilobular area or the area around the terminal or respiratory bronchioles can be recognized with HRCT. In addition, the authors confirmed that centrilobular emphysema and centrilobular tuberculous nodules can be diagnosed with HRCT. Thus, HRCT can demonstrate the location of pathologic changes within a lobule and may be helpful in the differential diagnosis of diffuse pulmonary diseases.