Background: Catechol-O-Methyltransferase (COMT) and Monoamine oxidase B (MAO-B) are the main enzymes that metabolize dopamine in the brain. The polymorphisms of the COMT gene and MAO-B gene are associated with high, intermediate and low levels of activity. This may influence the prevalence of motor complications in Parkinson's Disease (PD). Methods: The study enrolled 1087 Chinese PD patients throughout the country. Sanger dideoxynucleotide chain termination methods were used for COMT and MAO-B genotyping. The researchers compared the association between presence of motor complications and COMT and MAO-B gene polymorphisms, both separately and in combination. Results: Comparison of the allele frequencies revealed that COMT (GG) was significantly more common among PD patients who exhibited wearing-off compared to PD patients without wearing-off (P < 0.05). A statistically higher frequency of the MAO-B (AG) genotype in PD patients with dyskinesias was found (P < 0.05). Although these differences were not significant after Bonferroni's correction. The combined haplotype of the MAO-B and COMT showed no increase (p < 0.05) in the risk of wearing-off and dyskinesias. Conclusions: Our findings suggest that polymorphisms in COMT and MAO-B may increase the risk of wearing-off and dyskinesias. COMT (GG) genotype may be the risk factor of wearing-off. While MAO-B (AG) genotype may be the risk factor of dyskinesias. (C) 2014 Elsevier Ltd. All rights reserved.