Parkinsons disease (PD) is the second most common neurodegenerative illness diagnosed in the United States. Dementia is recognized to be common in PD, occurring in 19-78% of patients depending upon the definition used. The cognitive syndrome of Parkinsons disease dementia is predominantly one of executive dysfunction, and it has a profile that is distinct from Alzheimers dementia. Neuropsychiatric problems frequently accompany Parkinsons disease dementia and lead to considerable therapeutic challenges. This review focuses on the epidemiology, clinical characteristics, pathology, neuroimaging, diagnosis, and treatment of Parkinsons disease dementia.