The distinctive neuropsychiatric features of Alzheimer's disease (AD), dementia with Lewy bodies (DLB), and frontotemporal dementia (FTD) were investigated by using the Neuropsychiatric Inventory. The patients with FTD had significantly more euphoria, aberrant motor activity, and disinhibition and significantly fewer delusions compared with the patients with AD or DLB. The patients with DLB had significantly more hallucinations compared with the AD or FTD patients. The findings clearly demonstrate that AD, DLB, and FTD have distinctive neuropsychiatric features, which may correspond to different patterns of cerebral involvement characteristic of these three major degenerative dementias.