Usefulness of high-resolution computed tomography (HRCT) in locating pulmonary parenchymal disease in relation to the pulmonary lobule was evaluated in 71 patients, including 30 with normal pulmonary parenchyma and 41 with various pulmonary diseases. Both 10-mm-thick sections and 1.5- or 3.0-mm-thick HRCT scans were obtained. Distribution of pulmonary parenchymal disease was classified as centrilobular, panlobular, perilobular, bronchovascular, or nonlobular. Intralobular classification of disease distribution was more feasible in less severely diseased regions. HRCT revealed thickened intralobular bronchovascular bundles in patients with bronchiolitis obliterans, mycoplasma pneumonia, and pulmonary tuberculosis and thickening of both bronchovascular bundles and perilobular structures in patients with sarcoidosis, lymphangitis carcinomatosa, and malignant lymphoma. Centrilobular areas of increased attenuation were seen in patients with bronchopneumonia and pulmonary cryptococcosis. Centrilobular emphysema and bronchiolectasis were recognized only on HRCT images. The improved clarity and sharpness of parenchymal abnormalities on HRCT images, even in severely involved areas, provide additional information about disease distribution.