BACKGROUND: . Cognitive-behavioral therapy and mindfulness-based stress reduction (MBSR) are two prominent evidence-based treatments for social anxiety disorder (SAD). It is not clear, however, whether outcomes of these two treatments are moderated by similar factors. For example, whereas anger suppression and anger expression each predict outcomes in cognitive- behavioral group therapy (CBGT), it is unknown whether they differentially influence outcomes in CBGT versus MBSR. METHODS: . One hundred eight participants with SAD were randomized to CBGT, MBSR or Waitlist (WL). WL participants were later randomized to CBGT or MBSR, and their data were combined with data from those originally randomized to CBGT or MBSR. Anger suppression and anger expression were assessed at pre-treatment, and social anxiety was assessed at pre-treatment, post-treatment, and every 3 months throughout a 12-month follow-up period. RESULTS: . From pre- to post-treatment, higher anger suppression was associated with significantly greater reduction in social anxiety in CBGT compared with MBSR. From post-treatment through follow-up, higher anger expression was associated lesser reduction in social anxiety in MBSR but not in CBGT. LIMITATIONS: . Data are limited by sole reliance on self-report and it is unclear whether these findings generalize beyond group-based interventions. CONCLUSIONS: . Individuals with SAD who are higher in anger suppression and/or expression might be better suited to CBGT than MBSR.