After adjusting for covariates, compared to the healthy control group with the COMT (rs4633) T/T+C/T combined genotype as the reference group, the COMT (rs4633) risk C/C was significantly related to the risks of oral cavity and pharynx cancers (AOR = 1.78, 95% CI = 1.11–2.85) and the risk of OPMD (AOR = 2.65, 95% CI = 1.19–5.88). This evidence concerns the gene COMT and oculopharyngeal muscular dystrophy.