The objective of the study was to find out whether the school-based prevention programme `Initiated abstinence' is suitable to induce pupils to change their consumer behavior and attitudes. The participants of the prevention programme commit themselves `per contract' to abstain from or considerably reduce their consumption of at least one of their currently used substances (e. g. sweets, cigarettes) or media (TV, computer games) for a period of 2 weeks. The main goal of the programme is to sharpen their problem and health consciousness concerning addiction and pleasure seeking. The programme was evaluated by a longitudinal study. At three given times, the 12- to 15-year-old pupils of the experimental classes were interviewed by standardized self-completion questionnaires (n = 2,267). The control classes were submitted to two surveys (n = 586). The study was carried out in the areas of Innsbruck (Austria), Schleswig-Holstein (Germany) and South Tyrol (Italy). Not all pupils were able to keep their intentions submitted in their contract, but 4 of 5 pupils had at least one positive experience with the renunciation (82%). There were `overall effects': The actual renunciation of the pupils was much higher than stated in their agreement. The experimental group showed significant reduction effects for pupils, who had successfully reduced or stopped use of a substance or medium. In a further step, it should be explored whether the programme is suitable also for older groups, i.e. for pupils older than 15 years. Moreover, the long-term effects of the programmes should be tested.