OBJECTIVES: Internet/computer based Cognitive Behavioral Therapies (iCBT/cCBT) might serve as a cost-effective alternative to face-to-face psychotherapies. The purpose of this study was to synthesize the quantitative evidence from randomized clinical trials (RCTs)  addressing the long term benefits of iCBT/cCBT for patients with depression and anxiety. METHODS: Previous studies published through November 2011 were retrieved from three electronic databases (Scopus, Pubmed, PsycINFO). The inclusion criteria were English-language RCTs involving participants with major depressive disorder/depressive symptoms, generalized anxiety disorder, social phobia, and social anxiety disorder. The iCBT/cCBT interventions were compared to either some other treatment or to no-treatment control groups that were followed for >1 year. Standardized effect sizes (ES) were calculated from sample sizes, means and standard deviations for the primary outcome measure that was most closely related to the principal disorder. A random-effects model was used to calculate pooled effect sizes ES across the studies. Leave-one-out sensitivity analysis was also performed. RESULTS: Of the 769 articles identified, 82 were considered for full text retrieval and 10 met all inclusion criteria. The pooled mean ES from the ten different RCTs from 3 different continents  showed no statistically significant difference when i-CBT/c-CBT  was compared to active control [Effect Size (ES), - 0.10 , 95% Confidence Interval (CI), -0.21 to 0.01].  In contrast, results were significant when compared to placebo control (ES, -0.37, 95% CI: -0.70 to -0.05). No significant benefits for i-CBT/c-CBT in the long-term were found in the therapist supported subgroup. Results were robust when sensitivity analysis was performed. CONCLUSIONS: Evidence regarding the long term benefits of i-CBT/c-CBT for reducing depression and anxiety in adults are weak.  Additional well-designed RCTs involving longer follow-up are needed in order to assess the long-tem effectiveness of this intervention.