Increasing research efforts are focused on nonmotor aspects of Parkinson's disease (PD). Depression, anxiety, compulsivity (dopamine dysregulation symptoms), and hallucinations/psychosis are among these disorders, and all complicate the management of PD with negative influences on quality of life. There is a strong overlap between depression and apathy and likewise, depression and anxiety can coexist and require careful pharmacologic management. Dopamine dysregulation syndrome is linked to medication use and most clearly associated with dopamine agonists. In contrast, although hallucinations and psychosis do not occur unless patients with PD are treated with dopaminergic drugs, medication doses do not directly relate to this problem. Functional neuroimaging provides an excellent resource for investigating these behaviors as well as their anatomical and neurochemical bases. New treatments are being developed, but there have been very few large-scale randomized clinical trials to test the relative roles of new or available agents for abating these problematic behaviors.