PURPOSE: To evaluate the differential findings of CT in the differention of pleural exudates and transudates. MATERIALS AND METHODS: One hundred and thirteen consecutive patients (113 effusions) underwent enhanced thoracic CT ; the scans were evaluated for the presence or absence and appearance of enhancing parietal pleural thickening and extrapleural fat thickening. Thoracentesis was performed to measure pleural and serum total protein andlactate dehydrogenase(LDH) values. Effusions were classified as exudates by using Light's criteria. RESULTS: Eighty-eight effusions were exudates and 25 were transudates. Eighty-three of the 88 exudates (93%) were associated with enhanced parietal pleural thickening ; seventy of the 88 (80%) were associated with extrapleural fat thickening. Four of the 25 transudates were associated with parietal pleural thickening and extrapleural fat thickening, both of which were the most important factors in differentiating beteen pleural exudates and transudates(p<0.05). CONCLUSION: Parietal pleural thickening and extrapleural fat thickening on contrast-enhanced CT almost always in dicate the presence of pleural exudates.