Vascular cognitive impairment has been traditionally defined by structural pathology, an accumulation of infarcts, leading to progressive cognitive decline. Recent evidence, however, suggests that cognitive impairment may be independently mediated by hemodynamic dysfunction, including global and hemispheral hypoperfusion and altered cerebral blood flow regulation. In this review, we examine evidence for the contribution of hemodynamic impairment to cognitive dysfunction in the setting of large vessel disease, cardiac failure, and microvascular disease. If there is a hemodynamic component of vascular cognitive impairment, then treatments proposed to correct impaired vascular physiology may reasonably be expected to treat the cognitive dysfunction as well. © 2010 American Heart Association, Inc.