The current article explore genetic analysis of 24 Caucasian male subjects [12 PG patients and 12 healthy controls (HCs)] who had previously participated in a 11C-raclopride PET study involving gambling with a slot machine. Dopamine release during high-reward and low-reward gambling was quantified in a region of 52 voxels, where a statistically significant reduction in 11C-raclopride binding potential was observed (repeated measures ANOVA condition effect, voxel-level family-wise error-corrected P < 0.05), as described previously. PCR-based sequencing methods were applied to determine the genotypes of the C957T (rs6277) and G1101A SNPs in the dopamine receptor D2 gene (DRD2) and the TaqIA polymorphism in the ANKK1 gene from venous blood samples, as described previously. Subjects with the A1A2 genotype released significantly more dopamine during gambling than subjects with the A2A2 genotype. This finding suggests that TaqIA polymorphisms have influence on brain dopaminergic processing of reward or reward-related stimuli during gambling.