In studies on (premotor) Parkinson's disease (PD), single photon emission computed tomography (SPECT) studies have focused on imaging of the presynaptic dopamine transporter (DAT) and postsynaptic dopamine D2 receptors (D2Rs). Here we review the results of SPECT studies on the dopaminergic system in PD, with particular emphasis on: the accuracy of SPECT imaging of the dopaminergic system to detect alternations of the dopaminergic system in early PD, the diagnostic accuracy of DAT SPECT in PD, the contribution of DAT imaging to detect preclinical phases of PD, and the potential role of SPECT imaging to monitoring progression of dopaminergic degeneration in PD.