Nowadays cyberbullying prevention programs such as Surf-Fair can significantly reduce cyberbullying but little is known about necessary and sufficient conditions of their effectiveness. Case Study 1 followed three successive waves of implementation of Surf-Fair in one German highest-track secondary school in a pre-post design. Results show no reduction in negative cyber incidents, but students indicated using better coping strategies afterwards and evaluated Surf-Fair positively. These effects were more pronounced in later waves conducted by teachers, confirming teachers' ability to administer Surf-Fair. Case Study 2 explored if a stand-alone Surf-Fair Bystander Unit would successfully increase empathy and helping and reduce negative cyber incidents at German mixed-track comprehensive schools. No significant effects were detected in a pre-post waiting-control-group design, most likely due to the context. Based on these examples more general challenges of cyberbullying prevention research will be discussed, for example school volunteering and politics and different evaluation and didactic approaches.