PURPOSE: To evaluate the morphological differences between malignant and inflammatory lesions that arise from the cecal or pericecal region on CT by analyzing not only the mass itself but also the changes of surrounding structures. SUBJECTS AND METHODS: We reviewed CT scans of 38 cases of cecal lesions confirmed by pathology(16 malignant lesions and 22 inflammatory lesions). The analytical points were :the changes of bowel wall mass, the changes of surrounding structures, strands of retroperitoneal fat, pericecal fluid collection, and regional lymphadenopathy. RESULTS: The malignant bowel wall thickening(18.0mm) was thicker than inflammatory one(ll.4mm)(p < 0.001). Concentric bowel wall thickening was seen in 87.5%(14/16) of malignant lesions and 36%(8/22) of the inflammatory lesions. The pericecal fat stranding was circumferential in 84%(16/22) of inflammation and eccentric in 64%(916) of malignancy(p < 0.01). Pericolic fat infiltration was more extensive in inflammatory lesions(p < 0.005). The strands of retroperitoneal fat were more frequently found in inflammatory lesions(p < 0.05). The pericecal fluid collection was seen in 55%(12/22) of inflammatory lesions and none of malignant lesions. There was no difference in the presence of pericecal lymphadenopathy between the two groups. CONCLUSION: Malignant cecal masses have thicker and concentric bowel wall thickening, and narrower and eccentric pericolic fat infiltration. On the other hand, inflammatory masses have relatively thinner and eccentric bowel wall thickening, and more extensive and circumferential pericolic fat infiltration sometimes accompanied by abnormal fluid collection.