Aims: The objective of this study was to evaluate the preventive effect of a clinic-based, emotionally arousing, negative information giving intervention on adolescents' protective and risk factors of smoking. Methods: Data of 563 students (18 schools) from a cluster randomized controlled trial conducted in Heidelberg, Germany (2010-2011) were analysed. The intervention included a presentation about the risks of smoking, a live video session of a pulmonary endoscopy and a testimonial interview with a lung cancer patient. A prevention booklet served as the control condition. Students' reaction to the intervention was assessed after 2 weeks, risk and protective factors of smoking and smoking status were assessed after 2.5 months. Findings: The clinic intervention received significantly better ratings of credibility, personal relevance and emotional arousal than the booklet. Differences between clinic and booklet groups failed to reach significance on smoking-related threat appraisal, coping appraisal, protection motivation, behavioural intention and smoking status. Conclusions: Although the clinic intervention generated a significant immediate reaction, there were no significant preventive effects at follow-up. These results are in line with previous research and add further evidence for the ineffectiveness of emotionally arousing negative information giving in smoking prevention with adolescents.