Internet-based interventions have emerged as a new treatment and intervention modality for psychological disorders. Given their features of treatment flexibility, anonymity and confidentiality, this modality may be well suited in the management of addictive behaviours. A systematic literature review of the effectiveness and treatment outcomes of Internet-based interventions for smoking cessation, problematic alcohol use, substance abuse and gambling was performed. Studies were included if they met the following criteria: clients received a structured therapeutic Internet-based intervention for a problematic and addictive behaviour; included more than five clients; effectiveness was based on at least one outcome; outcome variables were measured before and immediately following the interventions; had a follow-up period; and involved at least minimal therapist contact over the course of the program. Sixteen relevant studies were found; nine addressed the effects of Internet-based interventions on smoking cessation, four on gambling, two on alcohol and one on opioid dependence. All studies demonstrated positive treatment outcomes for their respective addictive behaviours. The current review concluded that Internet-based interventions are effective in achieving positive behavioural change through reducing problematic behaviours. This mode of therapy has been found to have the capacity to provide effective and practical services for those who might have remained untreated, subsequently reducing the barriers for help-seekers. This in turn provides imperative information to treatment providers, policy makers, and academic researchers.