OBJECTIVE To evaluate high resolution CT (HRCT) in the diagnosis of diffuse pulmonary nodules. METHODS Fifty normal chest radiographs, conventional CT and HRCT were used to evaluate the visualization of pulmonary lobule. The configuration, distribution and intrinsic structure of lesion in 38 patients with diffuse pulmonary nodules were analyzed by HRCT. RESULTS The chest radiographs were not able to show the structure of pulmonary lobule. The visualization rates of pulmonary lobule were 20% by conventional CT and 50% by HRCT (P < 0.05). Of 38 patients with diffuse pulmonary nodules, 19 had interstitial nodules which were located in the pulmonary intestities, the lobular septa and under the pleura. HRCT could clearly show their para-bronchial distribution with clear cut margin. Four had airspace nodules, chiefly shown as solidification of the air spaces. There was no nodule beneath the pleura or in the lobular septa. HRCT revealed even density and hazzy margins. Fifteen had randomly distributed nodules, with the nodules scattered at random. HRCT showed nodules with high density, sizes varying greatly but the margin was clear. CONCLUSION High resolution CT is able to show the pattern of distribution, intranodular structures and background of the diffuse pulmonary nodules, which is valuable in the diagnosis and differential diagnosis of this disease.