<p>Substance use is a well-known public health problem among adolescents and emerging adults. Digital prevention components, oftentimes included in interventions to target substance use, offer unique possibilities and might be particularly suited for these age groups. However, thus far, a comprehensive overview of substance use prevention interventions utilising digital components is lacking. Hence, the overall aim of this study is to fill this research gap by identifying the type of digital components, their theoretical approaches and their combinations employed in substance use interventions for adolescents and emerging adults, and how the evidence base for their (individual) effectiveness was assessed. The literature was searched in four databases: MEDLINE, PsychInfo, CINAHL and Web of Science in May 2023. Inclusion criteria based on the PCC concept were: Population (adolescents and emerging adults aged 12–21&#xa0;years), Concept ((a) digital components of interventions AND (b) prevention or reduction AND (c) substance use), Context (all contexts). Studies were selected after title/abstract screening by two independent researchers. Data extraction included: substances and substance use behaviour, underlying theory/approach, characteristics of digital intervention components, methods used for evidence assessment, and study characteristics. These data were narratively summarised. 4,905 publications were screened and 176 were included, of which 114 reported on interventions with emerging adults and 62 with adolescents. These interventions were predominantly delivered in educational settings (86%), namely universities/(vocational)schools. Alcohol was the most commonly investigated single target substance (74%). The majority of all interventions were based on more than one theory/approach and it was not always clear which theories were combined. The most commonly reported approach in interventions for adolescents was the provision of information/education, for emerging adults, interventions were based on Social Norms Theory most frequently. The majority of interventions were delivered web-based. Randomized controlled study designs dominated, and evaluation was rarely performed separately for the intervention components. A variety of digital intervention components exist to reduce or prevent substance use among adolescents and emerging adults. However, different intervention components based on diverse theoretical approaches are often combined in one intervention and the individual effects of single components remain largely unmeasured. Future studies should consider innovative methods to analyse the effectiveness of individual components, and their possible interactions, within complex interventions. Combining effective digital components or adding these components to non-digital interventions could optimize the effectiveness of interventions for young people.</p>