A growing amount of evidence demonstrates that Endothelial Progenitor Cells (EPCs) are involved in adult neovasculogenesis and maintenance of vascular integrity. EPC decrease and dysfunction are related to atherosclerosis and cardiovascular disease (CVD), and it has been proposed that the level of circulating EPCs may be used as a surrogate index of cumulative cardiovascular risk. Moreover, many experimental approaches reveal that exogenous EPC injection stimulates blood flow recovery in critical limb and myocardial ischemia, providing a new therapeutic tool for CVD. Diabetes Mellitus is a clinical condition characterized by a high incidence of CVD and is indeed associated with alterations in EPC physiology. In this review we focus on the relationships between EPCs and vascular biology, with particular regard to Diabetes Mellitus and future therapeutical implications.