The effects of cerebrovascular lesions on DLB are not yet fully understood, whereas the development of Alzheimer's disease (AD) is known to be associated with cerebrovascular lesions. In this study, we investigated the frequency of concomitant cerebrovascular pathologies in autopsy-proven DLB cases (n = 25) in comparison with AD cases (n = 63). We also investigated the correlation between cerebrovascular pathologies and the clinical features of DLB cases. On gross inspection, five cases of DLB and seven cases of AD were complicated by cerebral hemorrhages and the difference was significant; most of the lesions in DLB were subdural hemorrhages, possibly related to trauma. Nine cases of DLB and 25 cases of AD had grossly identified infarctions, but no significant difference was observed. Three cases of DLB and four cases of AD had concomitant hemorrhages, while 10 cases of DLB and 43 cases of AD had infarcts on microscopic inspection. There was a significant difference in the frequency of microscopic infarcts between DLB and AD, whereas no significant difference was noted in the frequency of microscopic hemorrhages. In DLB cases without vascular complications, memory disturbance was common as the initial symptom, while parkinsonism was more common in those with vascular complications. However, no significant difference was observed between DLB cases with and without vascular complications with respect to the frequency of individual clinical symptoms over the whole clinical course. These findings suggest that grossly identified hemorrhages are more common in DLB because of trauma, while microinfarcts are less common in DLB than AD, although the reason remains unclear. Such vascular complications might affect the clinical manifestations, in particular, the initial symptom, of DLB.