Estimating the prevalence of cyberbullying among children of different ages is challenging. An examination of the literature finds that what is most notable about the research on prevalence is its variability. Factors such as a lack of a consensual definition of cyberbullying, and the rapid change in technology that limits our ability to generalize across studies of more than a few years, make these estimates even more challenging. Having said that, the literature suggests that between 20 and 40% of adolescents and between 9% and 25% of school age children are victimized online by bullies. At present, probably the only conclusion about prevalence that can be reliably drawn is that cyberbullying is neither extremely rare nor extremely common. It is frequent enough to be a legitimate source of concern. The causes of the difference in prevalence between older and younger children (whether these differences are large or small) may be due to differential access to technology (particularly mobile technology), cognitive limitations in younger children, and lower rates of education about cyberbullying in elementary and primary schools. Overall, there is a dearth of research examining younger children and cyberbullying.