Substance abuse significantly influences human health and may induce problems with social functioning worldwide. Numerous genetic and environmental risk factors, as well as their interactions, accelerate the development of drug addiction. Etiologically, the dopaminergic mesocorticolimbic reward pathways are related to psychoactive substance addiction, and the reward properties of heroin are connected with changes in the mesolimbic dopaminergic system. The aim of this study is a haplotypic analysis of subjects addicted to polysubstance. However, with the knowledge that this is not a homogenous subgroup, it was decided to separate and analyze homogenous subgroups of subjects in order to find specific haplotypic variants among them. The subjects in the subgroups were addicted to heroin, and subjects with more than two relapses in the past two years. The study group comprised of 301 polysubstance addicted rural male subjects. From this group, 2 homogenous subgroups of subjects were isolated and additionally analyzed: (1) a group of heroin addicted subjects (n=61), and (2) a group of heroin-addicted subjects with at least two relapses in the last two years (n=21). The group consisting of all polysubstance addicted rural subjects and both homogenous subgroups were analyzed against a control group of non-addicted subjects (n=300), matching gender and age. Five polymorphisms in the DRD2/ANKK1 region were analyzed: rs1076560, rs1800498, rs1079597, rs6276 in the DRD2 gene, and rs1800497 in the ANKK1 gene. A statistically significant haplotype association was found in analysis of the heroin addicted subjects, compared to controls, and two possible trends – when comparing the whole group of addicted subjects to controls, and in relapse subgroups, compared to the controls. The results obtained showed that haplotypes indicate a part of the biological component of addiction.