Background: To detect attention deficit hyperactivity disorder (ADHD) in treatment seeking substance use disorders (SUD) patients, a valid screening instrument is needed. Objectives: To test the performance of the Adult ADHD Self-Report Scale V 1.1(ASRS) for adult ADHD in an international sample of treatment seeking SUD patients for DSM-IV-TR; for the proposed DSM-5 criteria; in different subpopulations, at intake and 1-2 weeks after intake; using different scoring algorithms; and different externalizing disorders as external criterion (including adult ADHD, bipolar disorder, antisocial and borderline personality disorder). Methods: In 1138 treatment seeking SUD subjects, ASRS performance was determined using diagnoses based on Conner's Adult ADHD Diagnostic Interview for DSM-IV (CAADID) as gold standard. Results: The prevalence of adult ADHD was 13.0% (95% CI: 11.0-15.0%). The overall positive predictive value (PPV) of the ASRS was 0.26 (95% CI: 0.22-0.30), the negative predictive value (NPV) was 0.97 (95% CI: 0.96-0.98). The sensitivity (0.84, 95% CI: 0.76-0.88) and specificity (0.66, 95% CI: 0.63-0.69) measured at admission were similar to the sensitivity (0.88, 95% CI: 0.83-0.93) and specificity (0.67, 95% CI: 0.64-0.70) measured 2 weeks after admission. Sensitivity was similar, but specificity was significantly better in patients with alcohol compared to (illicit) drugs as the primary substance of abuse (0.76 vs. 0.56). ASRS was not a good screener for externalizing disorders other than ADHD. Conclusions: The ASRS is a sensitive screener for identifying possible ADHD cases with very few missed cases among those screening negative in this population.