Objective: To evaluate the effect of lisdexamfetamine dimesylate (LDX) on emotional lability (EL) in children with ADHD. Method: Post hoc analyses of a placebo-controlled trial of LDX-stratified children (aged 6-12 years) with ADHD to prominent and not prominent EL at baseline (score >3 or ≤3, respectively, on Conners’ Parent Rating Scale [CPRS] items of anger, loss of temper, and irritability). Efficacy was assessed by change in CPRS EL scores and ADHD Rating Scale-IV (ADHD-RS-IV) total and subscale scores. Safety measures included treatment-emergent adverse events (TEAEs). Results: LDX showed improvement versus placebo (p < .0005) for EL item least squares (LS) mean change scores at endpoint and throughout the day. At baseline, 138 and 73 participants randomized to LDX treatment and having baseline and endpoint CPRS scores were categorized with CPRS-derived prominent and not prominent baseline EL, respectively; 41 and 31 participants randomized to placebo were categorized with CPRS-derived prominent and not prominent baseline EL, respectively. ADHD-RS-IV total and subscale scores decreased with LDX regardless of baseline EL severity. TEAEs included decreased appetite, insomnia, upper abdominal pain, headache, and irritability. Conclusion: EL and ADHD symptoms improved with LDX regardless of baseline EL symptom severity. LDX demonstrated a safety profile consistent with long-acting psychostimulant use.(J. of Att. Dis. 2012; XX(X) 1-XX)