Persistent descending mesocolon(PDM)is caused by absence of fusion of the descending colon to the retroperitoneum. We report a case of laparoscopy-assisted surgery for descending colon cancer in a patient with PDM. An 88-year-oldfemale patient complaining of abdominal pain was diagnosed with bowel obstruction, and referred to our hospital. A computed tomography(CT)scan showed bowel obstruction due to descending colon cancer. After decompression of the colon by insertion of a transanal drainage tube, she underwent laparoscopy-assistedleft hemicolectomy. Intraoperatively it was observed that the descending colon was not fixed to the retroperitoneum, and the patient was diagnosed with persistent descending mesocolon. The accessory middle colic artery and the inferior mesenteric vein branched radially. In patients with PDM, the inferior mesenteric artery often branches radially. However, the various morphologies of branching of the accessory middle colic artery and the inferior mesenteric vein have not been reported. It is not clear whether the radial branching of the accessory middle colic artery and the inferior mesenteric vein is characteristic of patients with PDM. We should however expect radial branching of the accessory middle colic artery and the inferior mesenteric vein in such cases.