Relatively little is known about the interaction between behavioral changes, medication, and cognitive function in Parkinson's disease (PD). We examined working memory, learning and risk aversion in PD patients with and without impulsive or compulsive behavior (ICB) and compared the results with those in a group of age-matched control subjects. Parkinson patients with PD+ICB had poorer working memory performance than either controls or PD patients without ICB. PD+ICB patients also showed decreased learning from negative feedback and increased learning from positive feedback in off compared with on dopaminergic medication. This interaction between medication status and learning was the opposite of that found in the PD patients without a diagnosis of ICB. Finally, the PD group showed increased risk preference on medication relative to controls, and the subgroup of PD+ICB patients with pathological gambling were overall more risk prone than the PD group. Thus, medication status and an impulsive behavioral diagnosis differentially affect several behaviors in PD.