Objective: In two randomized controlled trials Titov et al. demonstrated significant benefit from an Internet- and email-based treatment programme for social phobia: the Shyness programme. Data are presented about the longer term outcomes (6 months after treatment), cost-effectiveness relative to face-to-face treatment, and the acceptability of the programme to participants. Method: Participants completed outcome and acceptability questionnaires at 6 months after treatment. Repeated measures analyses of variance were calculated using an intention-to-treat design. Cost-effectiveness in years lived with disability averted were calculated based on between-group effect sizes. Results: A total of 59% of treatment group participants completed the 6 month follow-up questionnaires. Between post-treatment and 6 month follow up participants continued to make improvements in symptoms of social phobia, while maintaining improvements in mood, psychological distress, and disability. At 6 month follow up the mean within-group effect size (Cohen's d) for the two social phobia measures increased from 1.2 to 1.4. Cost-effectiveness in years lived with disability (YLD) averted was calculated as one-quarter that of face-to-face group treatment, or $AUD1495 for one YLD gained, compared to $AUD5686/YLD gained. Participants rated the Internet treatment to be as effective and helpful as face-to-face treatment. Conclusions: The present results confirm the reliability of the short-term findings reported in the first two Shyness programmes. The procedure appears to be very cost-effective, and acceptable to participants. These data provide further support for the development of Internet-based virtual clinics for common mental disorders.