Background: Persistent descending mesocolon (PDM) is a case of colonic replacement and adhesion as a result of abnormal fixation of the gastrointestinal tract. In laparoscopic surgery, it is performed when the patient is in an unconscious state. However, laparoscopic surgery, especially robot-assisted surgery, may necessarily need to devise surgical procedures such as anatomical recognition and adhesion detachment. We herein report three patients with PDM that were treated with arthroscopic surgery at our hospital. Case presentation: Patient 1: a 73-year-old man with sigmoid colon cancer. Laparoscopic sigmoidectomy was performed, and there were no problems encountered (such as difficulty in recognizing the anatomical location) other than adhesion detachment. Robot-assisted surgery was performed to the other two patients. Patient 2: a 62-year-old man with lower rectal cancer and underwent an intersphincteric resection. Patient 3: a 76-year-old man with lower rectal cancer and underwent Hartmann's operation. The surgery duration of these patients took longer, the same with robot-assisted surgeries without PDM. Conclusions: Robot-assisted surgeries have a large magnifying effect on delicately removing adhesions, which is a characteristic of PDM. Also, some parts are difficult to grasp as a whole, and it takes time to recognize adhesions anatomically and to grasp the whole image. Here, we report our experience with laparoscopic surgery and robot-assisted surgery for left-sided colorectal cancer with PDM.