Background: bariatric surgeries especially laparoscopic sleeve gastrectomy (LSG) has achieved excellent results in treatment of morbid obesity. Using Multi detector computed tomography to evaluate gastric volume are more accurate and feasible when compared to the other methods.Aim: The study aims at correlation between the postoperative residual gastric volume and body weight reduction percentage.Methods This is a prospective observational study of twenty sleeve patients with morbid obesity who underwent LSG; they were investigated by MDCT after oral administration of Gastrographin solution mixed with bicarbonate sodium to distend the stomach with gas. The examination was done three months after operation. The remaining gastric volumes were estimated via 3D volume reconstruction.Results: The relation between the body weight reduction percentage and gastric volume estimated 3 months after the operation in the selected patients was negatively correlated, which means that the smaller the residual gastric pouch volume we have, the larger the weight loss will happen.Conclusion: MDCT allows important anatomical and accurate measurements about the relation between residual gastric volume and body weight reduction in sleeve gastrectomy-candidate obese patients.  So, with smaller residual gastric volume, we have more weight loss, but further studies are needed for longer period of time like 1 year period to confirm what we reached in this study.