The prevalence of diabetes mellitus (DM), particularly Type 2 DM, has rapidly increased in industrialized and many developing countries. The predominant cause of death in diabetic patients is vascular complications. Dyslipidemia and hypercholesterolemia are common in diabetic patients. 3-Hydroxy-3-methylglutaryl-CoA reductase inhibitors (statins) were designed for lowering cholesterol synthesis. Landmark clinical trials indicated that statins effectively reduced cardiac death and events in patients with coronary artery disease or DM. The benefits of statins on the prevention of vascular events were independent from age, sex or baseline lipid levels in diabetic patients. Statins not only prevent atherosclerotic macrovascular complications, but also postpone the development of microvascular complications of DM, such as nephropathy and retinopathy. The non-cholesterol lowering or pleiotropic effects of statins have attracted vast attention. Results from experimental and clinical studies suggest that statins may attenuate inflammation, oxidative stress, coagulation, platelet aggregation, and improve insulin resistance, fibrinolysis and endothelial functions and help to prevent thrombosis, restenosis or organ transplantation rejection. Statins may affect the intracellular prenylation of proteins, which modulate the activity of small-GTP binding proteins. This may be an underlying mechanism for some pleiotropic effects of statins. Statins have an excellent safety profile and seldom cause adverse effects. Increasing evidence suggests that statins are the current treatment of choice to prevent vascular complications in diabetic patients with hypercholesterolemia.