A retrospective study of a 50-year autopsy series of 900 patients with the clinical diagnosis of parkinsonism (31.2% with dementia) revealed pure Lewy body disease (LBD) in 84.9%, but only 44.7% with idiopathic Parkinson disease (PD); 16% were associated with cerebrovascular lesions, 14.8% with Alzheimer pathology; 8.9% were classified dementia with Lewy bodies (DLB), 9.4% showed other degenerative disorders, and 5.6% other/ secondary parkinsonian syndromes. The frequency of LBD during different periods was fairly stable, with increase of DLB and PD plus Alzheimer changes, but decrease of associated cerebrovascular lesions during the last decades. Using variable clinical diagnostic criteria not only by specified neurologists, the misdiagnosis rate ranged from 11.5 to 23% and was similar to that in most previous clinico-pathological studies. The majority of cases with false clinical diagnosis of PD had a final pathological diagnosis of DLB with or without Alzheimer lesions. A postmortem series of 330 elderly patients clinically diagnosed as parkinsonism with (37.6%) and without dementia showed that IPD, Braak stages 3–5 were rarely associated with cognitive impairment, which was frequently seen in IPD with associated Alzheimer pathology (35.5%), DLB (33.9%), and in Alzheimer disease (AD) or mixed dementia (17%), whereas it almost never was associated with minor cerebrovascular lesions.