 Parkinson s disease PD is a degenerative disorder of the nervous system. In PD, mainly the presynaptic dopaminergic neurons are affected: The dopamine synthesis as well as the active transport of dopamine into the synaptic gap by presynaptic dopamine transporters DAT is reduced. First parkinsonian symptoms occur when the concentration of dopamine within the basal ganglia is reduced by at least 80 per cent Bernheimer et al. 1973. The reduced DAT density represents a typical phenomenon of PD. The DAT density can be measured by means of nuclear medicine methods: the tracer FP-CIT Fluoropropyl-Carbomethoxy-Iodophenyl-Tropane has a high affinity to presynaptic DAT Booij et al. 1998. PD patients show a significantly lower striatal FP-CIT uptake than healthy controls. Therefore FP-CIT SPECT supports the diagnosis of PD Benamer et al. 2000. 