To evaluate the impact of a new Substance Use Disorder (SUD) education program on medical students’ attitudes, we selected the Substance Abuse Attitude Survey (SAAS) questionnaire, which we adapted to our curriculum and cultural context. To validate this adapted version, we conducted an exploratory factor analysis following the administration of our 29-item bSAAS questionnaire to 657 medical students in Belgium (response rate: 71.1%). Twenty-three items correlated to three factors; namely, “Stereotypes and moralism”, “Treatment optimism” and “Specialized treatment” were retained (70% of total variance explained, Cronbach’s alpha = 0.80) and constituted the new questionnaire called beSAAS. The factor “Specialized treatment” stood out from previous studies, which could be explained by our target population and the impact of the formal, informal and hidden curricula in medical education. This study was able to highlight certain factors influencing stereotypical representations such as age, gender, origin, personal or professional experience with substance use. Our study allowed us to retain the beSAAS as a good questionnaire to evaluate SUD stigma and highlighted interesting findings to improve SUD training in medicine. Further studies are needed to complete its validity and reliability.