The relative role of genetic and environmental factors in the pathogenesis of Parkinson’s disease (PD) has been the matter of investigation and debate, especially in the last 30 years. The possible interaction between genetic and environmental factors led to a great number of association studies between single nucleotide polymorphisms (SNPs) of many candidate genes and PD risk. In this study we summarized and critically reviewed the results of studies published on this issue, with especial reference to those reported in the last 5 years. Many studies provided conflicting findings and, when positive associations were identified, associations were weak. Polymorphisms related with activation or detoxification of drugs and xenobiotics, such as CYP1A1, CYP1A2, CYP19A1, CYP1B1, CYP2C9, CYP2C19, CYP2E1, CYP2D6, NAT2, GSTM1, GSTM3, GSTO1, GSTP1, PON1, PON2, ABCB1 and ADH genes have not been demonstrated convincingly a definitive association with the risk of developing PD. Nor did polymorphisms in genes related to dopamine or serotonin DRD, DAT, TH, DDC, DBH, MAO, COMT, SLC6A4, MTR, MTHFR, oxidative stress NOQ1, NOQ2, mEPHX, HFE, GPX, CAT, mnSOD, HFE, HO-1, HO-2, NFE2L2, KEAP1, inflammatory processes, ILs, TNF, ACT, NOS, HNMT, ABP1, HRHs, trophic and growth factors BDNF, FGF, or mitochondrial metabolism and function. In addition we analyzed other putative relations and genes associated with monogenic familial PD.Taking together the results of candidate gene association studies and genome wide association studies, only some SNPs of the MAPT, SNCA, HLA and GBA genes seem to be the most likely associated with PD risk.