We examined emotional responses in Attention Deficit Hyperactivity and Oppositional Defiant/Conduct Disorder to affective pictures. Eighty seven children (42 female, Mage = 11.2), with clinical or subclinical symptoms and controls viewed joy, fear, sadness or neutral pictures while heart rate, skin conductance, corrugator and zygomaticus responses were recorded. The moderating role of Callous-Unemotional and anxiety traits was evaluated. Lower resting heart rate and decreased skin conductance across picture types was associated with ADHD symptoms. Decreased heart rate reactivity to fear and sad stimuli was associated with ADHD and ODD/CD. Corrugator and zygomaticus responses were not associated with ADHD or ODD/CD. Findings are mostly consistent with a fearlessness account of disruptive behavior, and seem to also pertain to ADHD, with intact valence systems. Findings are discussed in light of the significance of identifying common pathogenic mechanisms across traditional diagnostic categories, consistent with trans-diagnostic approaches to the study of psychopathology. Copyright © 2018 Elsevier B.V. All rights reserved.