The development of imaging biomarkers which target specific sites in the brain represents a significant advance in neurodegenerative diseases and Parkinson's disease with the promise of new and improved approaches for the early and accurate diagnosis of disease as well as novel ways to monitor patients and assess treatment. The 3 major applications of imaging may play a role in Parkinson's disease include: 1) the use of neuroimaging as a biomarker of disease in order to improve the accuracy, timeliness, and reliability of diagnosis; 2) objective monitoring of the progression of disease to provide a molecular phenotype of Parkinson's disease which may illuminate some of the sources of clinical variability; 3) the evaluation of so-called ''disease-modifying'' treatments designed to retard the progression of disease by interfering with pathways thought implicated in the ongoing neuronal loss or replace dopamine-producing cells. Each of these areas has shown a numbers of critical clinical investigations which have better defined the utility of the imaging tools to these tasks. Nonetheless, current unresolved issues around the clinical role of neuroimaging in monitoring patients over time and validation of quantitative imaging measures of dopaminergic function are immediate issues for the field and the subject of current research efforts and the extension of the lessons learned in Parkinson's to other neurodegenerative diseases including Alzheimer's dementia.