Psychiatric problems such as mood and anxiety disorders are highly prevalent and are associated with high societal costs and individual suffering. Evidence-based psychological treatments obtain good results but are not available to the required extent due to the lack of practitioners with adequate training. One way to solve this problem is to provide minimal-contact self-help treatments, for example, with the assistance of computers. Recently, internet-delivered cognitive-behavioral treatment has been tested in a series of controlled trials. However, the interventions come in many forms with different levels and kinds of therapist input, which have implications for the costs of the treatments and possibly their effectiveness. In this review we found evidence for a strong correlation between therapist input and outcome. While emerging evidence attests to the efficacy of internet-delivered treatment when at least minimal therapist guidance is provided, most studies in the field have not included a formal evaluation of cost-effectiveness. Future research needs are discussed.