The links between ADHD and addictive disorders have been the subject of a large number of studies showing a high prevalence rate of ADHD in substance abusing populations as well as an increased risk of substance use disorder (SUD) in ADHD patients that may be independent of other psychiatric conditions. High prevalence of ADHD has also been highlighted among individuals suffering from other addictive disorders such as pathological gambling. Adequate diagnosis of ADHD in SUD patients is challenged by phenomenological aspects of addiction and by frequently associated other psychiatric disorders that overlap with key symptoms of ADHD. A detailed comprehensive search for child and adult symptoms including the temporal relationship of ADHD, substance use and other psychiatric disorders should maximize the validity and the reliability of adult ADHD diagnosis in this population. Further, a follow-up evaluation of ADHD symptoms during treatment of SUD may reduce the likelihood of misdiagnosis. Finally, it should be noticed that when SUD occurs with ADHD, it is associated with a greater severity of SUD compared to other SUD patients. This has been shown with an earlier age at onset, antisocial behavior, risk for depression, chronicity of substance use, need for hospitalization and likelihood of a complicated course. Recent data suggest that the effects of ADHD on SUD outcomes are independent of other psychiatric comorbidities. This highlights the need of an earlier implementation of preventive interventions for substance use or behavioral addiction in children/adolescents with ADHD and the necessity to consider this disorder in the treatment of addictive disorders. Benefices and risk of MPH in adult patients with addiction and ADHD are discussed.