This chapter presents the methodological design of the Sexting Behaviour study, which explores adolescent boys’ motivations and behaviours related to sexting. Using a two-stage sampling strategy, the study collected quantitative data through a custom questionnaire administered via a census approach in stratified school settings. Two cohorts were surveyed: the first (2016–2018) in a single Local Authority, and the second (2020–2022) across England with added regional stratification. In total, 3987 responses were gathered, enabling analysis across age, ethnicity, religion, sexual identity, and region. To ensure representativeness and reduce bias, the study used probability-proportionate sampling and aggregated responses. Adopting a pragmatic epistemological stance, it combined positivist and interpretivist approaches to capture both general trends and individual experiences. This dual perspective acknowledges the complexity of adolescent development and the subjective nature of sexting. The study’s rigorous design supports predictive validity and offers a nuanced understanding of sexting as a developmental, rather than purely behavioural, phenomenon.