Background Recognition of perigastric vessel anatomy is important to safely perform gastric surgery, especially in the case of laparoscopic gastrectomy. This study was designed to reevaluate the efficacy of preoperative three-dimensional (3D) angiography reconstructed from enhanced multidetector-row computed tomography (MDCT) data and to classify right gastric artery (RGA) branching patterns. Methods Perigastric vessel anatomy was preoperatively analyzed using MDCT-based 3D angiography reconstructed by computer software in patients undergoing laparotomic (n = 75) and laparoscopic (n = 25) gastrectomy. Results were compared with intraoperative findings in all cases, and were also compared with maximum intensity projection (MIP) imaging, which is similar to conventional angiography, in 10 patients. Results Preoperative diagnoses by 3D angiography were identical to intraoperative findings. The rates of branching patterns of the celiac artery and left gastric vein were comparable with previous reports. The detection rate of the right gastric artery (RGA) was 77.0 %. Branching patterns of the hepatic artery were classified into four types: right hepatic artery (RHA) ? left hepatic artery (LHA) type, replaced RHA ? LHA type, RHA ? replaced LHA type, and replaced RHA ? replaced LHA type. RGA ramification patterns were classified into three types according to hepatic arterial running patterns: distal (68.8 %), proximal (14.3 %), and caudal (16.9 %). Because of vessel overlapping, RGA ramified points were misdiagnosed under MIP images in two of ten cases (20 %). Conclusions Preoperative 3D angiography is useful for a new system of classifying RGA ramification patterns into three types. With this system, surgeons can perform laparoscopic gastrectomy with lymph node dissection more safely.