Ninety individuals with social phobia (social anxiety disorder) participated in a randomized controlled trial and completed cognitive-behavioral group therapy, exposure group therapy without explicit cognitive interventions, or a wait-list control condition. Both treatments were superior to the wait-list group in reducing social anxiety but did not differ from one another at posttest. Changes in estimated social cost mediated treatment changes in both treatment conditions from pre- to posttest. However, only participants who received cognitive-behavioral therapy showed continued improvement from posttest to 6-month follow-up, which was associated with a reduction of estimated social cost from pretest to posttest. These results suggest that cognitive intervention leads to better maintenance of treatment gains, which is mediated through changes in estimated social cost.