Individuals differ in the extent to which their vulnerability to anxiety is reduced by psychological therapy. However, the cognitive basis for such individual differences is still poorly understood. To test a cognitive account of differences in anxiety reduction in response to treatment, the present study examined individuals undergoing group therapy for social anxiety disorder. We assessed whether differences in their readiness to adopt selective attentional processing in response to an experimental contingency predicted positive changes in a range of anxiety measures in response to treatment. Findings were consistent with the position that readiness to alter attentional processing bias may underpin individual differences in the tendency to respond to positive experiential conditions, such as group therapy, by reducing anxiety vulnerability.