WHO Regional Office for Europe’s Mental Health Flagship is working with Member States to address the mental health needs of children and adolescents. This policy brief aims to support countries to formulate evidence-informed policy responses to the increasing influence of digital determinants on the mental health of young people in the WHO European Region. Evidence of the impact of technology use is mixed, with studies indicating both positive and negative associations between technology use and young people’s well-being. Some online activities also have both positive and negative effects simultaneously. However, the most vulnerable young people disproportionately experience negative impacts. The relationship between technology use and mental health is bidirectional: increased screen time potentially exacerbates mental health issues, which in turn may drive further technology use. Additionally, a variety of individual and environmental factors shape young people’s digital behaviours and experiences, which change over time. Based on this evidence, the brief suggests eight priority actions for countries to promote and protect the mental health and well-being of young people in digital environments, and to mitigate the potential harms related to social media, artificial intelligence and other digital technologies