PURPOSE: To compare the CT findings of peritoneal tuberculosis (PT) and peritoneal carcinomatosis (PC) based on the morphologic features of the peritoneum and assess the relationship between the degree of peritoneal thickness and the severity of omental infiltration in PT and PC. MATERIALS AND METHODS: We retrospectively reviewed the CT findings of 15 patients with PT and 14 with PC. We checked the morphologic changes of the peritoneum as seen on CT, for the following points: 1) the presence of peritoneal change: 2) the pattern of any change-diffuse thickening, plaque or nodularity, combined thickening (diffuse and plaque, or nodularity); 3) the degree of thickness on the whole peritoneum - mild (grossly definite, but not more than 3 mm), moderate (more than 3mm); 4) the presence of irregularity on the peritoneal surface. We also evaluated the significance of the relationship between peritoneal thickness and omental infiltration in both disease entities. The degree of omental infiltration was described as follows : grade I (no change or focal smudge pattern); grade II ( diffuse smudge), grade III (omental cake regardless extent). RESULTS: Peritoneal change was seen in 12 of 15 PT patients and in 7 of 14 PC patients. In all 12 PT patients, the pattern of change was diffuse thickening, and among the seven PC patients, there was diffuse thickening in one, plaque or nodular thickening in four, and combined thickening in two. In PT patients, the degree of thickness on the whole peritoneum was mild in six and moderate in six, and in PC patients it was mild in two and moderate in one. An irregular peritoneum surface was seen in one patient with PT and in two with PC. The degree of omental infiltration in PT was grade I in four patients, grade II in six andgrade III in five. In PC, it was grade I in six patients, grade II in two and grade III in six. Smooth diffuse thickening of the peritoneum was seen in 11 of 15 PT cases and in one of 14 PC (P<0.01). Accompanying plaque or nodularity was seen only in PC, in six of 14 patients (P<0.001). The relationship between the degree of peritoneal thickness and severity of omental infiltration was significantly proportional in PT (r=0.900, P<0.001), but not in PC (r=0.068, P>0.5). CONCLUSION: In PT and PC different CT findings based on peritoneal morphologic changes might be useful in differentiating these two entities. In addition, careful observation of relationship between the peritoneal change and the severity of omental infiltration is necessary.