Substance use disorders (e.g. substance addiction, substance abuse) and adult attention-deficit hyperactivity disorders (adult ADHD) are frequent psychiatric disorders with a high individual and social relevance. Complex interactions of common and divergent susceptibility genes and environmental factors are important for both disorders which have a relatively high heritability. Substance use disorders and adult ADHD are both associated with an increased risk for additional axis I disorders. The results of studies with respect to the comorbidity of adult ADHD and substance use disorders are inconsistent. Different hypotheses with respect to comorbidity are under discussion. A standardised diagnostic procedure has to be followed. The consequence of misdiagnosing adult ADHD with comorbid substance use disorder is that relevant specific therapeutic procedures will not be followed or stimulants will be prescribed too easily for individuals with substance use disorders. Multimodal integrated therapeutic concepts for the comorbidity of substance use disorders and adult ADHD have yet to be developed.