The identification of moderators of exposure-based cognitive behavior therapy (EXCBT) outcome has the potential to: (1) guide the judicious application of the limited resource of EXCBT, and/or (2) identify additional treatment targets for ameliorating the deleterious effects of an identified moderator, thereby enhancing clinical response. Experimental and clinical studies have provided intriguing findings for the moderating influence of positive affect on EXCBT outcomes. Mixed findings for state positive affect (at the time of extinction/exposure trials) as a predictor stand in contrast to evidence that baseline levels of trait positive affectivity may be a more effective predictor of EXCBT outcomes. As such, questions remain about the best way to assess positive affectivity as a potential treatment moderator. This study was designed to investigate: (1) the relative value of state and trait positive affect for predicting the outcome of a single-session virtual-reality exposure intervention for public speaking anxiety in college-aged adults, and (2) the role of three related constructs—optimism, hopefulness, and self-efficacy—that may explain the predictive significance of trait positive affectivity. State affect is manipulated at an experimental level with affect induction procedures; trait positive affectivity is measured at baseline. Three dependent measures–a primary outcome of public speaking anxiety and secondary outcomes of social phobia and self-reported valence--are examined. This study relies on a team science approach and is conducted across 14 collaborating sites through the Exposure Therapy Consortium, allowing for replication of all findings across diverse study sites across the world.