Although cognitive impairment after a posterior cerebral artery (PCA) infarct is frequently observed, the important functional areas associated with cognitive decline, other than the thalamus, have not been determined. We investigated the locus or loci that might induce cognitive decline after a PCA infarct. Forty-one patients with unilateral PCA infarctions involving only the occipital lobe or the occipital lobe plus other PCA areas were included. All subjects received a mini-mental status examination (MMSE) within 2 months of onset; 43.9% had cognitive impairment. The severity of cognitive impairment was not associated with left hemisphere lesion location, sex, age, education level, or the time between stroke and the MMSE assessment. Only the lesion volume was negatively correlated with MMSE score. Lesion location analysis revealed that an occipital plus splenial or parahippocampal lesion contributed to a decline in MMSE, which suggests that parahippocampal or splenial involvement with an occipital lesion is associated with the cognitive decline seen after PCA infarction.