PURPOSE: Mesenteric and omental cysts are uncommon lesions found all age groups. They elicit interest because of their unclear pathogenesis and confusing terminology. MATERIALS AND METHODS: CT findings of 12 case with mesenteric and omental cysts were described and compared with surgical and pathologic findings. RESULTS: In mesenteric and omental cyst, the histologic diagnoses were lymphangioma(7 cases), nonpancreatic pseudocyst(3 cases), mesothelial cyst(2 cases). Lymphangiomas were usually multiloculated with enhancing wall, located in the small bowel mesentery. And these cystic lesions were frequently attached to bowel and required resection of a bowel segment. In three cases of pseudocyst, thick and enhancing wall was shown in unilocular cyst. Two cases of mesothlial cyst were located in greater omenturn, showed very thin wall in unilocuation. CONCLUSION: The CT features of the mesenteric and omental cysts are fairly characteristic. Identification of lymphangioma, which shows a multilocuation and enhancing wall, is important due to frequent bowel resection in operative field.