Process-based cognitive behavior therapy (PB-CBT) may be informed by identifying shared mechanisms of disorder linked to shared processes of therapeutic change. Repetitive negative thinking (RNT) is a molar pathogenic process common to both generalized anxiety disorder and depression. Acceptance and commitment therapy (ACT) and metacognitive therapy (MCT) offer separate models of the relationship between RNT and emotional distress. In a pair of related studies, the relative degree to which processes specific to the two models accounted for variability in levels of generalized anxiety and depression in college student samples was evaluated. Across both studies, processes of cognitive fusion and obstructed valued living within the ACT model and beliefs about the negative consequences of RNT within the MCT model were most predictive of variability in levels of emotional distress. Limitations of this project as well as implications for further research and practice of PB-CBT for disorders of emotional distress are discussed.