The complexity of movement disorders poses challenges for clinical management and research. Functional imaging with PET or SPECT allows in-vivo assessment of the molecular underpinnings of movement disorders, and biomarkers can aid clinical decision making and understanding of pathophysiology, or determine patient eligibility and endpoints in clinical trials. Imaging targets traditionally include functional processes at the molecular level, typically neurotransmitter systems or brain metabolism, and more recently abnormal protein accumulation, a pathologic hallmark of neurodegenerative diseases. Functional neuroimaging provides complementary information to structural neuroimaging (e.g. anatomic MRI), as molecular/functional changes can present in the absence of, prior to, or alongside structural brain changes. Movement disorder specialists should be aware of the indications, advantages and limitations of molecular functional imaging. An overview is given of functional molecular imaging in movement disorders, covering methodologic background information, typical molecular changes in common movement disorders, and emerging topics with potential for greater future importance.