BackgroundThe Moti-4 intervention was developed to prevent addiction and other health problems among vulnerable adolescent cannabis users. The aims of Moti-4 are to reduce the use of cannabis among adolescents and to encourage their motivation to change their behavior.MethodsIntervention Mapping, a systematic approach to developing theory- and evidence-based interventions, was used to develop a protocol for the intervention. The process of developing the intervention also used the method of responsive evaluation to explore the opinions of the immediate target group and intermediaries (N = 31). Feasibility was assessed in 9 interviews and analyzed in grids.A quantitative pilot analysis involving a pre- and post-assessment in 31 subjects assessed whether the intervention was able to reduce drug use and would change intentions to change drug use behavior.ResultsUsing Intervention Mapping resulted in the development of a substantial four-session intervention with a clear manual and training for prevention workers. The choice of 12 consecutive steps was based on the Trans Theoretical Model of Behavior Change, Motivational Interviewing, Theory of Planned Behavior and the Self Determination Theory.Positive aspects of working with Moti-4 were assessed in a feasibility study. Criticism by users has led to improvements to the manual.In the pilot study, the average weekly amount spent on cannabis decreased significantly from an average €17.77 to €11,95 in the period after the intervention, with a medium effect size (d = 0.36). Likewise, a significant decrease was found in the frequency of use during the past week, from 4.3 to 2.4 (d = .52). As to motivation to change, a statistically significant increase was found in planning (d = .44) and a large increase in the desire to stop (d = .76). The change in the motivation to smoke less cannabis was small.ConclusionIntervention Mapping proved to be a useful approach for the development of the intervention, using a productive combination of theory and community knowledge. The pre- and post-test pilot study showed that the intervention generally brought about a considerable positive change in the two principle targets, cannabis use and motivation. There is a need for further (controlled) research into its effectiveness and implementation as a standard method in addiction prevention services.