Purpose: This paper aims to explore the prevalence rate of adolescents engaging in aggressive behaviours towards their peers using the Internet and mobile phones, while examining the duration and intensity of this cyberbullying, and to analyse differences in cyberbullying behaviours based on gender and age (academic grades). Research on cyberbullying indicates that it is a global problem that is increasing dramatically among adolescents. Design/Methodology/Approach: The sample was composed of 1,415 Spanish adolescents of both sexes (760 boys and 655 girls) between 12 and 17 years old (M = 13.9 years old; SD = 1.4). Findings: The results indicated that the cyberbullying prevalence among adolescents in the past year was 32 per cent. Likewise, the data suggest that boys and students in their fourth year of secondary education (15-17 years old) perpetrated cyberbullying on their peers more than girls and students in lower grades. Research Limitations/Implications: The results presented in this research should be interpreted with caution due to its cross-sectional nature; a longitudinal study with measurements at different times would help to confirm the results observed here. On the other hand, in this study, the adolescents' responses were obtained through self-reports and, although they could be subject to social desirability effects and biases, as indicated by Flisher et al. (2004), the reliability and validity of adolescent self-reports in the measurement of risk behaviours were quite acceptable. Practical Implications: It is of crucial importance to develop educational strategies designed to favour the responsible use of the new technologies. In many cases, children and adolescents are not aware of psychological and legal consequences that their cyber-aggressions can have on themselves, on the victims and on their families and social environment. Social Implications: The authors feel that this research may contribute to clarifying some crucial issues related to the growing problem of cyberbullying that affects adolescents in many countries of the world. As the present research deals with aspects of interactive technology and smart education, the authors believe that the findings reported in the manuscript would be of interest to potential readers of this Journal. Originality/Value: This paper is an original perspective on cyberbullying aggressors among secondary education students in a Spanish context.