We evaluated the CT findings of 21 cases of chronic diffuse lung disease which were diagnosed with open lungbiopsy(7), transbronchial lung biopsy(3), bronchoalveolar lavage(4), occupational history(2), skin biopsy(2),liver biopsy(1), bone marrow aspiration (1), clinical functional and radiographic findings(6). CT scans wereobtained by using 8mm collimation at 8mm intervlas in all patient, and additional high resolution CT scans(1mm collimation) were also obtained in 17 patients of them. Although the traditional classification method of diseasedistribution into upper, middle and lower zones was somewhat useful, the model of disease distribution proposed byBergin and Muller was more useful in evaluation of chronic diffuse lung diseases. The diseases that were mainlydistributed in axial compartment were lymphagitic carcinomatosis(5), sarcoidosis(2) and those in middlecompartment were silicosis(2), extrinsic allergic alveolitis(1), hypereosinophilic syndrome(1), unclassifiedone(1) and in periphearl compartment were fibrosing alveolitis (idiopathic pulmonary fibrosis(3), Rheumatoidlung(1), scleroderma(1), dermatomyositis(1), And in diffuse panbronchiolitis(3), even distribution of lesions toboth axial and peripheral compartments was noted. But infibrosing alveolitis, some degree of distribution wasnoted in peripheral compartment and in lymphangitic carcinomatosis and silicosis, some degree of distribution wasnoted in peripheral compartment. Nodular thickening of bronchovascular bundles was characteristically seen in allcases of lymphangitic carcinomataosis and sarcoidosis. The nodules were 1.5mm in diameter and were composed oftumor cells(in lymphangitic carcinomatosis) and of sarcoid granuloma within lymphatics in the bronchovascularsheath. However patients with sarcoidosis did not have irregular thickened interlobular septa and polygonal lines. Dilatation of peripheral airways without dilatation of proximal bronchi was only seen in diffuse panbronchiolitis.Although we experineced only two cases of silicosis, the nodules of silicosis were separated from the pleura at aconstant distance and seldom touched to the pleura.