Objective: To investigate the frequency of pathological gambling among alcohol and other substance abusers who sought specialized treatment. Methods: Seventy-four outpatients from three different substance abuse treatment services were interviewed. The South Oaks Gambling Screen (SOGS) scale was used for the diagnosis of pathological gambling. The diagnosis of alcohol and other substances abuse was established according to the DSM-IV criteria and the Short Alcohol Dependence Data (SADD) scale. The Portuguese version of the Self-Report Questionnaire (SRQ) scale was used to detect psychiatric symptoms and the Center for Epidemiological Studies Depression Scale (CES-D) for depressive symptoms. Average scores obtained from the application of these scales were compared using the Student t-test. Results: All subjects met the criteria for drug abuse, 61.6% met the alcohol dependence criteria, 60.3% for cocaine/crack, and 34.2% for cannabis. According to the SOGS scale, the majority of drug addicts (70.3%) were classified as social gamblers, 10.8% as problem gamblers and 18.9% as pathological gamblers. Psychiatric and depression symptoms were found in the sample. Pathological gambling patients showed more depression symptoms than non-pathological gambling patients. Conclusions: A high frequency of pathological gambling was found among the drug addicts interviewed. It is emphasized the importance of investigating pathological gambling among patients under treatment of drug abuse and to include strategies for the treatment of this disorder.