Background: By identifying which predictors and moderators lead to beneficial outcomes, accurate selection of the best initial treatment will have significant benefits for depressed individuals. Method: An automated, fully self-guided randomized controlled internet-delivered noninferiority trial was conducted comparing two new interventions (Interpersonal Psychotherapy FIFT; n=6201 and Cognitive Behavioral Therapy FCBT; n=6101) to an active control intervention (M00dGYM; n=613) over a period of 4 weeks to spontaneous visitors of an internet-delivered therapy website (e-couch). A range of putative predictors and moderators (socio-demographic characteristics rage, gender, marital status, education levell, clinical characteristics Fdepression!anxiety symptoms, disability, quality of life, medication usel, skills Fmastery and dysfunctional attitudesi and treatment preference) were assessed using internet-delivered self-report measures at baseline and immediately following treatment and at six months follow-up. Analyses were conducted using Mixed Model Repeated Measures (MMRM). Resu Its: Female gender, lower mastery and lower dysfunctional attitudes predicted better outcome at post-test and!or follow-up regardless of intervention. No overall differential effects for condition on depression as a function of outcome were found. However, based on time-specific estimates, a significant interaction effect of age was found. For younger people, internet-delivered 1Ff may be the preferred treatment choice, whereas older participants derive more benefits from internet-delivered CBT programs. Limitations: Although the sample of participants was large, power to detect moderator effects was still lacking. Conclusions: Different e-mental health programs may be more beneficial for specific age groups. The findings raise important possibilities for increasing depression treatment effectiveness and improving clinical practice guidelines for depression treatment of different age groups.