E-Mental Health Interventions for Harmful Alcohol Use: Research Methods and Questions 2.5 million yearly deaths and 4.6% of the global burden of disease are attributable to the harmful use of alcohol, according to the World Health Organization in 2011. Brief interventions have become increasingly valuable in the management of individuals with alcohol-related problems. The availability and uptake of these brief interventions is however limited. This so-called treatment gap may be narrowed through accessible, effective, and inexpensive treatment programmes. E-mental health interventions would be one promising approach for developing such treatment options, if they are shown to be effective. In this dissertation, the (cost-)effectiveness of two interventions based on cognitive behavioural therapy is subjected to research in three consecutive studies. The two interventions are a non-therapist involved Internet-based self-help programme, and a therapist led Internet therapy, based on textual-chat interaction. The aim of this dissertation is twofold. First, there is a clinical aim: to identify effective and cost-effective e-mental health interventions for harmful alcohol use. Second, there is a methodological aim: to address methodological challenges in the design, execution, and analysis of e-mental health randomized controlled trials. In the coming years, it is expected that the development and dissemination of e-mental health interventions will advance. This dissertation hopes to contribute valuably to the current knowledge base, upon which future research and interventions will build.