Objective: To examine the level of agreement between self- and observer-reported ratings of ADHD symptoms and executive function (EF) behaviors in adults with moderate to severe ADHD and EF deficits. Method: During a 10-week, randomized, double-blind, placebo-controlled study, the effect of lisdexamfetamine dimesylate (LDX) on EF was assessed by self-report and informant report (Behavior Rating Inventory of Executive Function–Adult Version), and ADHD symptoms were assessed by clinician- and informant-rated scales (ADHD Rating Scale IV with adult prompts and Conners’ Adult ADHD Rating Scales–Observer Report: Short Version, respectively). Post hoc analysis used Pearson correlations to assess relationships between self- and informant-rated EF and clinician- and informant-rated ADHD symptoms. Results: Correlations between self-ratings versus informant ratings and clinician versus informant ratings were greater at Week 10/early termination (EF: placebo [0.5231–0.6085], LDX [0.3543–0.5167]; ADHD symptoms: placebo [0.4169], LDX [0.4004]) versus baseline (EF: placebo [0.3208–0.5023], LDX [0.2852–0.3439]; ADHD symptoms: placebo [0.1511], LDX [–0.0408]). Conclusion: LDX improved EF and ADHD symptoms, based on participant, informant, and clinician ratings. Increased rater agreement over time may reflect improved symptom awareness. (J. of Att. Dis. XXXX; XX(X) XX-XX)