Addictive disorders are complex diseases influenced by both genetic and environmental factors. Heritability of these disorders is moderate to high. Genes that increase the risk of addiction to a substance actually increase the risk of addiction to other substances. This means it is mainly through broad externalizing pathways that genes increase the risk of addiction. The current level of our knowledge in genetics is less than enough to have clinical applications. Probably, in the near future, we will be able to provide our patients with individualized report about their susceptibility to addiction.