Objective To assess the significance of multi-detector row CT in differential diagnosis of the inguinal hernia and femoral hernia. Methods CT images which were reconstructed by multi-planer reconstruction （MPR） of 260 patients with inguinal hernia and femoral hernia who treated in our hospital form Oct. 1， 2012 to Oct. 31， 2013 were analyzed retrospectively， for exploring the relationship between sac and anatomic structure in the groin area. Results There were 146 patients with indirect hernia （75 in right， 60 in left， and 11 in bilateralism）， 82 patients with direct hernia（39 in right， 34 in left， and 9 in bilateralism）， and 32 patients with femoral hernia （17 in right and 15 in left）. The 157sacs of patients with indirect hernia originated lateral to the inferior epigastric artery， entered the inguinal canal and through the deep ring， which mainly located anterior （103/157， 65.6%） or anteromedial （36/157， 22.9%） to the spermatic cord or round ligament. The 91 sacs of patients with direct hernia originated medial to the inferior epigastric artery， and mainly located medial to the spermatic cord （70/91， 76.9%）. Sacs of both indirect hernia and direct hernia located anterosuperior to the inguinal ligament. The 32 sacs of patients with femoral hernia located posterior to the inguinal ligament and inside the “radiological femoral triangle” of coronal views. Conclusions The MPR images available from multi-detector row CT permit the accurate diagnosis of groin hernias. By using simple anatomical criteria， direct hernia， indirect hernia， and femoral hernia can be reliably distinguished．