Attention-Deficit/Hyperactivity Disorder (ADHD) is one of the most common neurodevelopmental disorders of childhood, characterized by persistent symptoms of inattention and/or hyperactivity and impulsivity that negatively impact social and academic functioning (APA, 2013; CDC, 2018b). Adolescents with ADHD commonly exhibit symptoms of trait anxiety, which can contribute to a decreased ability to effectively react to stress (Oh et al., 2018; Weems et al., 2005). Research has indicated that executive functioning also plays an important role in the regulation of stress (Ward et al., 2015), which suggests that adolescents with and without ADHD may respond differently to stressful situations given the variability in executive functioning profiles between these two populations (Kofler et al., 2018). The current study aimed to explore this further by examining how executive functioning moderates the relationship between trait anxiety and stress regulation in adolescents with and without ADHD. This study used data from the Cognition and Neuroimaging in Teens (CogNiT) Study conducted at UNC Chapel Hill. Participants included 40 adolescents aged 9-16 years old who had a previous diagnosis of ADHD (N=18) or who were typical controls (N=22). Executive functioning processes, including cognitive flexibility, inhibitory control, and working memory, were measured using standardized neuropsychological assessments. Trait anxiety was measured using the Spielberger State-Trait Anxiety Inventory for Children (STAI-C; Spielberger, Edwards, Montuori, & Lushene, 1973). Stress regulation was measured using average respiratory sinus arrhythmia (RSA) assessed at five timepoints before, during, and after participation in the Montreal Imaging Stress Task (MIST; Dedovic et al., 2005). Results indicated between-group differences in RSA withdrawal, as well as differences in the relationship between trait anxiety and RSA withdrawal. Moderation effects of executive functioning were examined using multilevel modeling (MLM). Cognitive flexibility was found to have a significant moderating effect on the relationship between trait anxiety and stress regulation for both groups. No significant effects were found for inhibitory control or working memory. The results of this study contribute to our understanding of how higher order cognitive processes such as executive functioning influence physiological responses to stress in adolescents with and without ADHD. Implication...