8 patients with pathlolgically proven pleural mesothelioma(5 localized type 3 diffuse type), and 1 patient with malignant pericardial mesothelioma were examined by computed tomog-raphy(CT) and obtained some results as follows: 1. Pleural Mesothelioma a. Localized pleural mesothelioma 4 cases were benign and 1 case was malignant in microscopic examination. CT showed invariably sharply marginated pleura-based soft tissue mass and the density of the mass was variable homogenous in small tumor but injomogenous with low density area in larger ones and even calcification was seen in one of them. The angle of pleura-mass interface was obtuse in only one small tumor and acute with smooth tapering end in four larger tumor. b. Diffuse pleural mesothelioma(DPM) Multiple nodular pleural masses encompassing nearly entire lung were seen with associated multiple subplerual parenchymal nodule & localized axial interstitial thickening in two case. Protruding chest wall mass with destruction of rib was seen in previous pneumonecto-mized thorax. Minimal pleural effusion/thickening was also seen in all. 2. Pericardial mesothelioma Pericardial fluid and multiple nodular masses which occupied pericardial sac up to duperior sinus were well delineated on CT. It had been misinterpreted as pericardial effusion for years on echocardiogram.