Consensus diagnostic criteria for dementia with Lewy bodies (DLB) proposed in 1996 have provided a useful foundation for research in the field. As a clinicopathologically defined entity, DLB has overlapping features of both Alzheimer s disease (AD) and Parkinson's disease (PD). Consensus criteria for DLB distinguish it from PD dementia by the earlier appearance of motor signs in the latter. Studies evaluating the standardized clinical diagnostic criteria for DLB have generally found them to be highly predictive of Lewy body pathology. However, many cases with Lewy body pathology and concomitant pathological features of AD elude clinical detection. Emerging data suggests that AD pathological features mask the clinical expression of concomitant Lewy body pathology, and that DLB and PD dementia may be more similar than distinct.