It is estimated that one in fifteen cases of dementia is caused by diabetes. However, very little is known about the way diabetes influences cognitive functioning. The results of this dissertation suggest that high blood glucose levels (to a greater extent) and vascular factors such as high blood pressure and arterial stiffness (to a lesser extent) contribute to differences in the cognitive function of people with and without type 2 diabetes. At the same time, these factors only go a small way towards explaining the differences in cognitive performance in people with diabetes.