ObjectiveTo investigate the relationship between β-amyloid (Aβ) deposition and striatal dopamine depletion, cognitive functions, and neuropsychiatric symptoms in dementia with Lewy bodies (DLB).MethodsWe consecutively recruited 51 patients with DLB who had undergone a neuropsychological test, Neuropsychiatric Inventory assessment, brain MRI,N-(3-[¹⁸F]fluoropropyl)-2β-carbon ethoxy-3β-(4-iodophenyl) PET, and¹⁸F-florbetaben PET within 6 months. The patients were divided into Aβ-negative (DLB-Aβ−, n = 20) and Aβ-positive (DLB-Aβ+, n = 31) groups according to the brain amyloid plaque load score. We performed comparative analyses of dopamine transporter (DAT) activity, neuropsychological profile, and neuropsychiatric symptoms between the 2 groups.ResultsCompared to the DLB-Aβ− group, the DLB-Aβ+ group had a younger age at diagnosis (p= 0.017), poorer performance in attention (p= 0.028) and visuospatial (p= 0.006) functions, and higher proportion of anxiety (p= 0.006) and total neuropsychiatric burden (p= 0.013). Those in the DLB-Aβ+ group also had lower DAT activity in the anterior putamen (p= 0.015) and ventral striatum (p= 0.006) regardless of age, sex, and years of education. In addition, lower DAT activity in the ventral striatum was significantly associated with anxiety and total neuropsychiatric burden in DLB.ConclusionsThis study demonstrated that Aβ deposition in DLB is associated with diagnosis at a younger age, higher cognitive and neuropsychiatric burden, and decreased DAT activity, suggesting that evaluation of clinical features and DAT activity can predict the presence of Aβ in DLB.