Colonic J pouch anal anastomosis is widely employed after rectal resection. In the 36 patients who participated in our retrospective study, although postoperative continence was retained/maintained in each individual, a survey questionnaire indicated some difficulties in neoanorectal function. Therefore, defecography was performed in 20 of these patients. Patients experiencing soiling were found to have an increased ano-pouch angle and pelvic floor descent. Loss of sensation and incomplete evacuation were also associated with an abnormally large pelvic floor descent. However, stool frequency, urgency, and the need for medication showed no correlation with any of the defecography parameters. These findings thus suggested that the puborectal muscle and the levator ani muscle played an important role in postoperative function. Defecography was also found to provide a dynamic assessment of the postoperative state of colonanal reconstruction.