INTRODUCTION: As the prevalence of substance use continues to rise all over the world amidst the ongoing pandemic, substance use prevention professionals are challenged to find alternative ways to enhance their knowledge and competence to use the best practices in the field. In the present global health situation, in which running face-to-face training seminars is extremely difficult, the most feasible option is through online learning. The aim of this study is to explore how the different aspects of a substance use prevention online course affected the overall effectiveness of the programme. ...