Over the last decade, the importance of cognitive impairment and dementia in Parkinson's disease (PDD) has been increasingly recognized. Investigators have proposed criteria for PD dementia, and mild cognitive impairment. Risk profiles associated with the development of dementia based on demographic, neurological, neuropsychological, imaging, and genetic investigations have been delineated. The FDA has approved a treatment for PDD, and efforts now are directed toward intervention at earlier stages of cognitive impairment.