<p>Generalized Anxiety Disorder (GAD) typically develops during adolescence and is one of the most prevalent disorders in youths. However, the remission rates associated with treatments indicate substantial room for improvement. An important next step is to more precisely identify modifiable maintenance factors that can be targeted in treatment. Drawing on research in adults, two theoretical models have gained prominence in informing the conceptualization and treatment of adolescent GAD: The Intolerance of Uncertainty model and the Metacognitive model. These models emphasize different knowledge structures as the central maintenance factor of GAD, where the former assigns central importance to intolerance of uncertainty beliefs and the latter to negative metacognitive beliefs about worry. However, empirical studies comparing their contributions to GAD symptoms in adolescents are limited. Hence, the current study aims to assess the relative contribution of intolerance of uncertainty beliefs and negative metacognitive beliefs about worry as statistical predictors of anxiety, depression and chronic worry in a sample of 117 adolescents with analog GAD. Three hierarchical linear regressions were conducted, one for each of the symptom categories. Negative metacognitive beliefs about worry accounted for independent and unique variance across all outcomes, whereas intolerance of uncertainty beliefs only made an additional contribution to anxiety symptoms. These results imply that negative metacognitive beliefs about worry are the most reliable correlate of symptoms and chronic worry in adolescents with analog GAD, and that formulating and modifying them has the potential to improve formulation and intervention strategies.</p>