Evidence on e-therapy for the treatment of substance use disorders and other addictions was from a small number of systematic reviews (SRs) and randomized controlled trials (RCTs). Findings consistently showed that therapist-guided e-therapy was superior to no treatment and wait list in reducing alcohol consumption or cannabis use, and the effect was small. Therapist-guided e-therapy was found to be equivalent to no treatment and wait list for patients with gambling addiction. With respect to substances, evidence was limited to the treatment of problematic alcohol and cannabis use and it is therefore unclear if the results generalize to the misuse of other substances. The evidence on gambling was limited to those who participated in online video poker.