Diabetes is a chronic metabolic disease which can lead to numerous complications. One of these disturbances is cognitive function impairment. A group of 62 patients with type 1 and type 2 diabetes. There is a correlation between certain clinical features among diabetic patients and cognitive functions. Negative influence on cognitive functions have a higher level of total cholesterol, a higher level of LDL cholesterol, a lower level of HDL cholesterol concentration in the blood, a higher level of glucose after meals, a higher level of basic insulin dose and insulin dose taken just before the examination, longer duration of the diabetes and a lot of hypoglycemic episodes. There is no influence on cognitive functions from glucose levels before meals, the type of the insulin therapy, or the number of hyperglycemic episodes and value rate of hemoglobin HbA1_C.