Neuropathies are one of the most common complications in diabetic patients. Several studies determined relationship between cognitive disorders and diabetes mellitus (DM). The historical cohort study was designed to distinguish relation of DM and cognitive decrements. The Wisconsin Card Sort Test (WCST) and Mini-Mental Status Exam (MMSE) were conducted for evaluation of cognitive problems. Fifty diabetic patient and 48 control participants were included to study. Exposure and no-exposure groups had no significant difference regarding sex, age and educational level. Cognitive problems were 8 times more in diabetics than control group (RR=8.2 %95CI=2.15 -31.4). Such as differences were in color, shape, and combined items between two groups. The MMSE results were not significant differences between both groups. The findings of our study strongly confirmed relationship between DM and cognitive decrements. These results have been shown in previous studies by different investigators.