Behavioral and psychological symptoms of dementia (BPSD) bother patients with dementia with Lewy bodies (DLB) and their families so frequently that early diagnosis of DLB before the appearance of prominent cognitive impairment is important. Because BPSD in DLB can be reduced or improved by early intervention, medical intervention is important. Of BPSD in DLB, vivid visual hallucinations and delusions are most important. Other visual cognitive impairments and sleep disturbances, including disorders in rapid eye movement (REM) sleep, are also frequently seen. Cholinesterase inhibitors, including donepezil chloride, are the first choice for the therapy of BPSD; Yokukansan (a type of Kanpo (traditional Chinese herbal) medicine) is the second choice. When neither treatment is effective, atypical antipsychotics, such as quetiapine, risperidone, and aripiprazol, may be used.