Abstract: Objective: To evaluate the diagnostic value of CT colonography (CTC) in detection of transperitoneal invasion from gastric cancer. Method: Eight gastric carcinoma patients underwent CTC for preoperative work-up. Although no obvious peritoneal nodule was seen on axial CT images, colonic wall deformities were noted on three-dimensional (3D) air images. Multiple Planar Reconstruction (MPR) images revealed thickening colonic wall at the deformities, and in addition, we also observed dense cordlike structures which connecting the primary gastric cancer and colonic wall thickening. Results: on one hand, cordlike indurations consistent with peritoneal invasion were found to connect the primary gastric cancer, gastrocolic ligament, and transverse mesocolon during exploratory surgery. On the other hand, we observed colonic scars consistent with peritoneal invasion. Conclusion: All of observations suggest that CTC could be use for the differentiation of gastric cancer and transperitoneal colonic invasion.