This report presents the findings from an experience sampling method (ESM) study conducted in Belgium and Finland . The aim of this study was to examine adolescents’ situational and daily information and communications technology (ICT) use and its associations with wellbeing . In both countries, the study was conducted in two waves, during the early and late autumn 2022, respectively. In addition, a supplementary data collection was carried out in Finland in spring 2023. The data consists of 17,671 momentary and daily questionnaire responses from 456 participants . The participants were 13- to 17-year-old adolescents (63% girls) from seven different schools. ESM, a momentary survey method, was used to collect data in situ with participants’ mobile phones. Four momentary and two diary questionnaires were administered during the 14-day data collection period in each wave. The method allows assessing experiences and behaviour that are situational and context-specific, reducing retrospective bias. Moreover, ESM ...