Epidemiological evidence suggests a reduced incidence of many common types of cancers in individuals with Parkinson's disease (PD). Parkinson's disease and cancer are two diseases that result from an excessive signaling by one of two forces driving cells to opposite directions. PD results from the excessive death of dopaminergic neurons in the substantia nigra pars compacta (SNc) in the brain, while uncontrolled growth is the key property of cancer. Parkinson's disease is a complex disorder, probably due in most of the cases to the interaction of environment and genes. Many genes responsible for familial forms of PD are supposed to have a supportive role in regulating or maintaining the cell cycle, a fact that allows us to assume their interaction in tumorigenesis. Understanding the nature of these processes may help researchers find new and more efficacious therapeutic approaches for both diseases.