Although Parkinson's disease is defined by its motor symptoms, the symptoms that are most devastating to patients and caregivers are dementia and psychosis. In addition, sleep has a tremendous impact on patient well being and quality of life. Eighty percent to 90% of Parkinson's disease patients have a sleep disorder affecting their ability to fall asleep, ability to stay asleep, dreams, motor activity during sleep, post-sleep behavior, or day-time somnolence. Treatment plans for patients with Parkinson's disease who experience sleep disorders aim to improve nighttime sleep or daytime wakefulness, and treatment options vary by sleep disorder.