Dementia with Lewy bodies (DLB) is a clinically and neuropathologically defined syndrome and the second cause of dementia in elderly individuals. In addition to the presence of Lewy-related pathology (Lewy bodies and neurites), Alzheimer's disease(AD)-type neuropathologic changes such as senile plaques and neurofibrillary tangles are frequently present. In this review, the author focused on the co-occurrence of pathologic changes of DLB and AD. However, in order to understand recent concepts of dementia, clinicians need to realize that multiple brain pathologies are common in elderly patients.