CT findings of 120 cases of renal fascial thickening were analyzed to appraise the meanings of renal fascial thickening and to seek the findings which are helpful for the differential diagnosis. Causes of fascial thickening were 46 inflammation, 40 neoplasm, 17 retroperitoneal hemorrhages and 17 retroperitoneal lymphadenopathy. Six cases were intraperitoneal pathology including each 3 cases of hepatocellular carcinoma and subhepatic abscess. Incidence of fascial thickening in acute pancreatitis was 35% and almost all of them were complicated pancreatitis. Ten of 27 pancreatitis and 7 of 17 lymphadenopathy showed bilateral fasical thickening with more tendency to left side. Only right side thickening was noted in 6 cases of pancreatitis. Anterior fascial thickening was prominent in anterior pararenal disease but 11 cases of pancreatitis showed posterior fasical thickening too. In renal disease, posterior fascial thickening was more prominent. In pancreatitis and lymphadenopathy renal fascia was more diffusely thickened but in tumorous condition and renal inflammatory disease, the thickening was more localized. In anterior pararenal disease the fascia was thickened or blurred on outside but in renal disease it was inside, so the space where the lesion originated could be suggested. Repeated CT scans after treatment showed that the degree of thickening improved as the primary disease improved.