We investigated the neuropsychological correlates of hippocampal atrophy in Parkinson's disease (PD) patients. The memory impaired PD patients had smaller hippocampi than other PD patients. The performance of PD patients in spatial working memory and attentional set-shifting correlated with the severity of motor defect, and not with hippocampal atrophy. Our results suggests that failure of verbal/visual memory may be related to hippocampal atrophy in Parkinson's disease. On the contrast, the defect in spatial working memory and attentional set-shifting may be sensitive to dysfunction of 'fronto-striatal' systems in PD patients.