In DLB, limbic pathology contributes to the cognitive difficulties of DLB, but little is known about the role of the hippocampus. We sought to determine whether the density of α-synuclein, tau and amyloid-β pathology in hippocampal subregions is associated with baseline cognitive performance in dementia with Lewy bodies (DLB). Patients with clinically probable DLB were followed prospectively until autopsy (n=49). Quantitative image analyses of α-synuclein (LB509), tau (PHF-1) and amyloid-β (4G8) density in the CA1, CA2/3, CA4 and subiculum regions of the hippocampus were carried out. A Memory and Naming composite score was composed of the mean age-adjusted scaled scores of Logical Memory delay, Auditory Verbal Learning Test delay, and Boston Naming Test. An Attention and Visual composite score was composed of the mean age-adjusted scaled scores of Trail Making A, Stroop Word, Rey Complex Figure copy, and Block Design. Spearman rank correlations between pathology and cognitive composite and individual tasks were carried out. Mean duration of illness was 7 ± 3 years, mean age at death was 75 ± 7, and baseline mean MMSE was 23 ± 4. Deposition of tau and amyloid-β was greatest in the subiculum and CA1, while deposition of α-synuclein was greatest in the subiculum and CA2/3 (p<0.01). The Memory and Naming composite was correlated with tau in the CA1 (r = -0.35, p<0.01) and subiculum (r = -0.41, p<0.01), with α-synuclein in the subiculum (r= -0.47, p<0.01), and with amyloid-β from all hippocampal sectors (but strongest in the subiculum, r = -0.45, p<0.01). The Attention and Visual composite score was correlated with α-synuclein in the subiculum (r= -0.31, p=0.03) and in CA2/3 (r = -0.30, p=0.03). Memory and naming difficulties were associated with a greater burden of tau and amyloid-β in the CA1 region, and with greater α-synuclein, tau and amyloid-β in the subiculum. Worse attention and visual processing performance was associated with greater α-synuclein density in the subiculum and CA2/3 hippocampal subregions, a pattern that may be related to the dense interconnectivity to neighboring limbic regions known to be affected in DLB.