A number of benign and malignant diseases may cause pleural abnormalities. Since the resolution of computed tomography(CT) has been improved, the detailed anatomy of pleura can now be well delineated in various pleural diseases. We reviewed retrospectively the CT findings of 60 patients with patholofically proved pleural diseases in order to find out the differential points between benign and malignant diseases. Thirty-six patients had malignant diseases(20 adenocarcinoma, 8 squamous cell carcinoma, 4 small cell carcinoma, 2 lung metastasis, 1 large cell carcinoma, 1 small and large cell carcinoma), and 24 patients had benign diseases(16 tuberculosis including empyema, 3 bacterial empyema, 3 pneumonia, 1 lung abscess, 1 lung contusion). The CT features that suggested malignant pleural diseases were high-grade mediastinal involvement(57.9%, p<0.1), thick and irregular thickening with nodularity and mass formations(38.5%, P<0.1), Circumferential pleural thickening 132.1%, P<0.01), and aggressive pleural effusion 122.2%, p<0.05). Benign pleural lesions were typically represented by pleural calcification(50%) and extrapleural fat accumulation(45.8%)