PURPOSE: To demonstrate the two-phase spiral CT features of pseudo-wall thickening and tumor in the gastricantrum, and to evaluate the possibility of differential diagnosis by analyzing two-phase spiral CT scans. MATERIALS AND METHODS: We retrospectively reviewed 120 cases in which two-phase spiral CT scans showed focal wallthickening in the prepyloric antrum of the stomach. Our series included 60 cases of gastric cancer (includingseven of early gastric cancer) and 60 cases of normal prepyloric antrum. All patients underwent two-phase spiralCT and upper gastrointestinal series (n=83) and/or gastric endoscopy (n=80). All cancer cases were confirmed bybiopsy (n=60). We evaluated the differential points between gastric cancer and pseudo-wall thickening of thegastric antrum. RESULTS: The mean thickness of the antral wall was 19.0mm in the cancer group and 12.5mm in thenormal group. Thirty-one cases (51.7%) in the cancer group and 51 (85.0%) in the normal group showed concentricwall thickening, while in each group, the remainder showed eccentric wall thickening. The common enhancementpatterns of thickened wall in the cancer group were 1) a thick enhanced mucosal layer during the arterial phase,with diffusely enhanced whole wall thickness during the venous phase (n=21); 2) a thick enhanced mucosal layerduring the arterial phase, with thicker and more intense enhancement of the same area during the venous phase(n=18). In the normal group, the common enhancement pattern was a thin enhanced mucosal layer during both thearterial and venous phase (n=34). In the cancer group, the common associated findings were regionallymphadenopathy (n=43) and food remnants in the stomach (n=15), and in the normal group, intraluminal normalmucosal folds in the thickened segment (n=50). The findings of food remnants despite overnight fasting andintraluminal normal folds occurred only in the cancer and normal group, respectively. CONCLUSION: Pseudo-wallthickening frequently showed thin enhancement of the mucosal layer on both the arterial and venous phases oftwo-phase spiral CT scan; a tumor frequently showed a thick enhanced mucosal layer during the arterial phase, withdiffusely enhanced whole-wall thickness during the venous phase or a thick enhanced mucosal layer during thearterial phase, with thicker and more intense enhancement of the same area during the venous phase. The finding ofthin and homogeneously enhanced intraluminal normal mucosal folds in the thickened segment strongly suggested thatthe lesion was a pseudo-lesion.