Early differential diagnosis of parkinsonism is of paramount therapeutic and prognostic importance. In the present review, the diagnostic value of routinely used nuclear medicine procedures is presented and critically discussed. The [(123)I]FP-CIT single-photon emission computed tomography (SPECT) is the method of choice for differentiation between neurodegenerative and non-neurodegenerative parkinsonism. The [(18)F]fluorodeoxyglucose positron emission tomography ([(18)F]FDG-PET) method provides a very high diagnostic accuracy for differentiating between Parkinson's disease (PD) and atypical Parkinsonian syndromes (APS), which is clearly superior to the accuracy of [(123)I]FP-CIT SPECT, [(123)I]IBZM SPECT and [(123)I]MIBG scintigraphy. Furthermore, [(18)F]FDG-PET is the only of the aforementioned techniques that also allows a reliable differentiation between APS subgroups (e.g., multiple system atrophy, progressive supranuclear palsy and corticobasal degeneration). Current studies are investigating the probable value of [(18)F]FDG-PET for risk stratification of dementia in PD.