As the Internet becomes increasingly ubiquitous and mobile, Internet addiction appears as a potential mental health problem in adolescents and students. From the reported negative consequences, it appears Internet addiction can have a variety of detrimental outcomes for young people that may require professional intervention. The unique contribution to knowledge of this research is (i) the assessment of the interplay between certain personality traits and the usage of specific Internet applications in contributing to an elevated risk of Internet addiction in two independent samples of 3,105 adolescents in the Netherlands and 2,257 university students in the UK, (ii) the development and testing of the concise Internet addiction components model using the quantitative data obtained, and (iii) the phenomenological exploration of the presenting problem of Internet addiction from the perspective of 20 psychotherapists from Europe, the USA, and Canada. A mixed methods approach was used in the form of psychometric measurement and qualitative interviews. Data were analysed using logistic regression, confirmatory factor analysis, structural equation modelling, and interpretative phenomenological analysis. The results of the empirical studies indicate that (i) Internet addiction symptoms are prevalent in approximately 3% of the included adolescent and student populations, (ii) certain personality traits and Internet application usages are risk factors for Internet addiction, (iii) the Internet addiction components model may facilitate initial assessment, and (iv) the presenting problem of Internet addiction is relevant for contemporary psychotherapeutic practice. Overall, this research supports the American Psychiatric Association’s decision to include Internet Gaming Disorder as distinct condition in the appendix of the revised diagnostic manual (DSM‐5), with beneficial consequences for treatment, research, and prevention efforts. Conclusively, additional support is offered for understanding Internet addiction as disease, not as a transient and easily dispensable by‐product of a technophilic generation’s new media consumption.