Lewy bodies were originally described in isolated brainstem nuclei in persons with Parkinson's disease. They have since been recognized as a widespread and common neuropathologic finding in individuals with dementia. Dementia with Lewy bodies (DLB) is the preferred term for the dementia syndrome associated with Lewy bodies. Although DLB is acknowledged as the second most common degenerative dementia, trailing only Alzheimer's disease, its ranking with respect to vascular dementia remains controversial. Large, community-based studies of DLB with postmortem confirmation are lacking. Available data suggest that DLB is more common than pure vascular dementia but not more common than any vascular contribution to dementia.