The gene coding for the dopamine receptor D3 (DRD3) is considered as a major candidate gene in various addictive disorders. Association studies in alcohol-dependence for this gene are nevertheless controversial. We made the hypothesis that phenotypical heterogeneity of alcohol-dependence (i.e. the DRD3 gene is a vulnerability gene in a specific subgroup of patients only) could explain these spurious findings, focusing on a core dimension of addictive disorders, namely impulsiveness. In our sample of 108 French alcohol-dependent patients, patients above the median value for cognitive impulsiveness (one of the three dimensions of the Barratt scale) were more frequently heterozygous than both alcohol-dependent patients with lower impulsiveness (OR = 2.51, P = 0.019) and than 71 healthy controls (OR = 2.32, P = 0.025). Age at interview, antisocial personality disorder, other comorbid addictive disorder, age at onset of alcohol-dependence, and lifetime mood disorders did not constitute confusing intermediate factors.