Smokers with both lower miR-29b and higher DNMT3B mRNA expression levels (OR 5.12, 95% CI 2.64–9.91), and smokers with both higher miR-29b and higher DNMT3B mRNA expression levels (OR 6.88, 95% CI 3.27–14.46) had an evident risk of lung cancer. The gene discussed is DNMT3B; the disease is lung cancer.