Objective To evaluate the value of multi?slice CT?based tumor predominant feeding artery sign in the localization diagnosis of exophytic tumors in the pancreaticogastric space. Methods CT images of 34 patients with pathologically proven exophytic tumors located in the pancreaticogastric space including 20 gastric gastrointestinal stromal tumors (GIST) and 14 pancreatic tumors, 7 patients of neuroendocrine neoplasms (NEN) and 7 patients of solid pseudopapillary neoplasms (SPN) were retrospectively analyzed. Two radiologists identified the tumor feeding arteries of the tumors and made the localization diagnoses. The inter?observer agreement was evaluated by Kappa coefficient. Chi?square test or Fisher exact test was used to compare the visualization of tumor predominant feeding artery sign in the two groups. Results The tumor feeding arteries were identified in 19 of 20 gastric GISTs and 13 of 14 pancreatic tumors. The two observers had a good agreement on the origins of the tumor feeding arteries (Kappa coefficient: 0.681). There was statistically significant difference in the origins of the tumor feeding arteries between the two groups (χ2=23.86,P<0.01). The blood supplies of most GISTs originated from gastric arteries, while those of most pancreatic tumors originated from the pancreatic branch of splenic artery. The tumor predominant feeding artery sign was identified in 17 gastric GISTs (17/20, 85.0%) and 11 pancreatic tumors (11/14, 78.6%). There was no statistically significant difference in the positive rate of the sign between the two groups (P=1.000). For all tumors enrolled, the sensitivities, specificities, accuracies, positive predictive values, and negative predictive values of the sign for the localization diagnosis of gastric GISTs and pancreatic tumors were 85.0% (17/20), 92.9% (13/14), 88.2% (30/34), 94.4% (17/18), 81.3% (13/16) and 71.4% (10/14), 100.0% (20/20), 88.2% (30/34), 100.0% (10/10), 83.3% (20/24), respectively. Conclusion The tumor predominant feeding artery sign on multi?slice CT can assist in the localization diagnosis of gastric and pancreatic exophytic tumors in the pancreaticogastric space.