Cyber-bullying is a phenomenon inextricably linked to the problematic use of new technologies and the Internet. If the more traditional bullying practice is a form of delinquent behaviour that creates grave psychosocial problems to the bullied victims then, cyber-bullying has even more negative effects towards the victim, and as we’ll see furthermore, the teenager is disparagingly exposed to an unsupervised online environment. A fact that channels into them intense negative feelings difficult to deal with. The present paper will attempt to highlight all aspects of cyber-bullying, what distinguishes it from the more traditional one, its forms, in addition to the already existing research data on the cyber-bullying phenomenon. Moreover, it will be first time showcased an important segment of nationwide research involving teenagers living in public facilities of child protection in Greece, regarding the use of internet and cyber-bullying. In this research, to boot, the profiles of both the victims and the offenders of cyber-bullying were examined, the causes leading the offenders to bully, and the reasons the victims believe they themselves acceded to online violence. Finally, in the conclusions the profile of teenagers living in public facilities of child protection will be discussed and the reasons leading them to deviating online behaviours, as a recap of the causes possible to lead a teenager to cyber-bullying and juvenile delinquency.