Parkinson's disease (PD) is one of the most common neurodegenerative disorders, affecting about 1% of the population over the age of 60. In addition to motor abnormalities, there are several non-motor signs and symptoms that may create a considerable burden for patients and care-givers. Dementia is common and affects approximately 40% of PD patients during the course of the disease, the risk for the development of dementia being 6 times higher than in non-PD age-matched controls. In most cases, PD patients with dementia (PDD) display a dysexecutive syndrome and visuospatial deficits, while memory is relatively unaffected. The overlap between PDD and dementia with Lewy bodies suggests that they likely share similar underlying neuropathological processes.