Although chronic constipation is common, colonic functional evaluating tests are uncommon. This study examines whether chronic constipation and gastrointestinal symptoms are correlated with the lateral diameter of the colon measured from MRI images. We included chronic constipation patients in a prospective, cross-sectional study using MRI at three centers. We divided 3D MRI colorectal images into 6 segments using with specified sequences and selected the maximum luminal diameter from each segment. We used the GSRS questionnaire to evaluate gastrointestinal symptoms. We evaluated the correlation between luminal diameters and GSRS scores. We found the following positive correlations: descending colon and unsatisfactory defecation symptoms; sigmoid colon and diarrhea; and rectum and constipation. The sum and ratio of the ascending and sigmoid colon diameters correlated with nausea and diarrhea. The sum of the transvers to the sigmoid colon diameter also correlated with nausea and diarrhea. The sum of all segment diameters correlated with nausea and constipation. In conclusion, we showed cross-sectional study of colonic MRI correlate with gastrointestinal symptoms. MRI might be useful for colonic motility evaluations to determine appropriate constipation treatments (Clinical trial registry number UMIN 000021274).