Today, 463 million people worldwide suffer from diabetes, while 374 million have prediabetes. Unfortunately, this number is expected to double by 2030. However, data about the prevalence of diabetes are influenced by the age group to which it refers. For example, in 2000, 12% of people between 65 and 70 years old as well as 15% of the over 80s were affected by diabetes. Nowadays, the percentage of over 65s with diabetes is about 20-25%, with some geographical differences. Dementia is another critical health problem which is greatly increasing especially among the elderly. While it is well known that diabetes is a significant risk factor for worsening vision, renal function, and increased risk of cardiovascular disease, a number of recent epidemiological evidence reported that diabetes can also be considered a risk factor for cognitive dysfunction. Therefore, while basic research and trials on human models are focused on understanding the pathophysiological mechanisms underlying the development of cognitive decline in individuals with diabetes, in clinical practice the prevention of cognitive decline in the individual with diabetes is critically important. In this paper, we will discuss the pathogenetic mechanisms, clinical approach, and diagnostic strategies that can be used in a clinical-ambulatory setting for early diagnosis of cognitive decline in patients with diabetes.