Treatment of Parkinson's disease (PD) is improving and we can choose a variety of drugs and surgical procedures for appropriate stages of the disease. However, we depend upon clinical signs and symptoms as well as patient reports to evaluate such issues. While neurochemical research into the etiological aspects of PD has been expanding, imaging is still under investigation. Here, I summarize the results of studies with regard to imaging of dopaminergic systems, and discuss the key points for imaging of PD with respect to treatment evaluation.