Objective: The purpose of this study is to provide reliability and validity evidence of the Adult Self-Report Scale (ASRS) scores on different versions and scoring procedures in a Spanish substance use disorder (SUD) sample. Method: The sample was made up of 170 outpatients diagnosed with SUD. The ASRS, the Mini-International Neuropsychiatric Interview (MINI), and the Substance Dependence Severity Scale were administered. Results: The results of the confirmatory factor analysis (CFA) showed adequate fit to the structure proposed by the Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV) in the 18-item version. On the screening scale, best fit was found for a model with two correlated factors (inattention and hyperactivity). The exploratory factor analysis (EFA) showed that the ADHD items converge and are differentiated from symptoms of withdrawal. The regression analyses showed that severity of dependence is explained by the ASRS scores. Conclusion: Both versions of the ASRS showed adequate psychometric properties. The polytomous or dichotomous score is relevant in patient classification.