BACKGROUND AND OBJECTIVES: Mindfulness-based interventions (MBIs) are proposed to cultivate trait mindfulness through mindfulness practice, which may in turn to lead improved clinical outcomes. Individuals who report lower levels of this trait may be promising candidates for MBIs because they present with the opportunity for growth in this area. Attention-Deficit/Hyperactivity Disorder (ADHD) has been associated with low trait mindfulness, though facets of trait mindfulness and ADHD features beyond core symptoms have not been examined among youth with the disorder. The goal of this study was to examine trait mindfulness-including facets of trait mindfulness-in adolescents with and without ADHD in relation to ADHD symptoms and related ADHD characteristics. METHODS: Adolescents (29 ADHD, 30 non-ADHD) and their caregivers completed measures of ADHD symptoms and related characteristics. Adolescents completed a trait mindfulness measure. RESULTS: The ADHD group scored significantly lower than the non-ADHD group in trait mindfulness. ADHD symptoms and multiple related characteristics were also inversely associated with trait mindfulness. A series of regressions controlling for sex and age indicated that trait mindfulness-particularly acting with awareness-is inversely associated with ADHD symptoms, cognitive disengagement syndrome symptoms, executive functioning, and sleep. CONCLUSIONS: Trait mindfulness, particularly acting with awareness, is lower among adolescents with ADHD and is inversely associated with ADHD and related characteristics. Because mindfulness is thought to be particularly therapeutic for those low in trait mindfulness, findings indicate the need to develop MBIs for adolescents with ADHD.