Smoking behaviors, including heaviness of smoking and smoking cessation, are known to be under a degree of genetic influence. The enzyme catechol O-methyltransferase (COMT) is of relevance in studies of smoking behavior and smoking cessation due to its presence in dopaminergic brain regions. While the COMT gene is therefore one of the more promising candidate genes for smoking behavior, some inconsistencies have begun to emerge.We explored whether the rs4680 A (Met) allele of the COMT gene predicts increased heaviness of smoking and reduced likelihood of smoking cessation in a large population-based cohort of pregnant women. We further conducted a meta-analysis of published data from community samples investigating the association of this polymorphism with heaviness of smoking and smoking status.In our primary sample, the A (Met) allele was associated with increased heaviness of smoking before pregnancy but not with the odds of continuing to smoke in pregnancy either in the first trimester or in the third trimester. Meta-analysis also indicated modest evidence of association of the A (Met) allele with increased heaviness of smoking but not with persistent smoking.Our data suggest a weak association between COMT genotype and heaviness of smoking, which is supported by our meta-analysis. However, it should be noted that the strength of evidence for this association was modest. Neither our primary data nor our meta-analysis support an association between COMT genotype and smoking cessation. Therefore, COMT remains a plausible candidate gene for smoking behavior phenotypes, in particular, heaviness of smoking.