Aims: Addiction treatment training has been recognized to be an essential part of the curriculum in psychiatry and general medicine. Our objective in this study was to measure the knowledge and attitudes towards addictions among medical residents of a general hospital in Catalonia, Spain. Methods: Within a sample of medical residents, we administered a questionnaire based on previous literature including attitudes towards patients with drug use problems, evaluation of knowledge and beliefs about harm reduction policies. Additionally, basic professional data, and personal as well as family consumption history were recorded. Findings: Four dimensions were found within the beliefs of medical residents about drug treatment and training: judgement of medical treatment of addictions and harm reduction, attitudes toward patients, importance given to training and assessment of training received. When correlating these dimensions with personal characteristics, we found those residents with personal or family history of drug use to have higher positive attitudes towards patients with addictions, and also better predisposition towards harm reduction policies. Residents working with these patients tended to give more importance to training and knowledge, and to have a better perception of the training already received, compared with residents without this contact. Conclusions: Although residents working often with addicted patients appear to have positive attitudes towards addiction treatment, according to our results, it seems very important to improve training policies, awareness and attitudes towards addiction among the whole medical community.