Introduction: Sleep-related problems are common in children with attention-deficit/hyperactivity disorder (ADHD). Sleep disorders are also side effects of all stimulant ADHD medications. Serdexmethylphenidate/dexmethylphenidate (SDX/d-MPH) is a once-daily treatment approved for patients age 6 years and older with ADHD. In this analysis, sleep behavior was assessed during SDX/d-MPH treatment in children with ADHD., Methods: In a 12-month, dose-optimized, open-label safety study in 6- to 12-year-old participants (NCT03460652), a secondary endpoint was assessment of sleep behavior based on the Children's Sleep Habits Questionnaire (CSHQ) consisting of 8 sleep domains (bedtime resistance, sleep onset delay, sleep duration, sleep anxiety, night wakings, parasomnias, sleep-disordered breathing, and daytime sleepiness). This post hoc analysis examined the individual sleep domains in the 12-month safety study., Results: Of 282 participants enrolled, 238 were included in the sleep analysis. At baseline, mean (SD) CSHQ total sleep disturbance score was 53.4 (5.9). After 1 month of treatment, the mean (SD) CSHQ total score significantly decreased to 50.5 (5.4); least-squares mean change from baseline was -2.9 (95% CI: -3.5 to -2.4; p < 0.0001) and remained decreased up to 12 months. Mean sleep-score improvements from baseline to 12 months were statistically significant ( p < 0.0001) for 5 of 8 sleep domains, including bedtime resistance, sleep anxiety, night wakings, parasomnias, and daytime sleepiness. Parasomnias and daytime sleepiness sleep domains showed the greatest mean improvement from baseline to 12 months. Sleep onset delay and sleep duration scores increased from baseline to 12 months. No statistically significant worsening occurred from baseline in sleep duration and sleep-disordered breathing domains; however, worsening of sleep onset delay was statistically significant., Conclusion: In this analysis of children taking SDX/d-MPH for ADHD, sleep problems did not worsen based on the mean CSHQ total sleep disturbance score. Statistically significant improvements in most CSHQ sleep domains were observed after 1 month and lasted for up to 12 months of treatment., Competing Interests: GM discloses that in the last 3 years he received consultant fees or honoraria from AbbVie, Acadia, Alkermes, Avanir, Axsome, Boehringer Ingelheim, Eisai, Emalex, Ironshore, Intra-Cellular Therapies, Janssen, Lundbeck, Medgenics, Neos, Neurocrine, NLS-1 Pharma AG, Otsuka, Redax, Rhodes, Roche, Sage, Shire, Sunovion, Supernus, Takeda, Teva, and Tris Pharma. ACC discloses that she in the last 3 years acted as a consultant for Aadrvark, Arbor, Aytu, Ironshore, Neos Therapeutics, Neurocentria, Noven, Otsuka, Purdue, Rhodes, Sky, Sunovion, Tris Pharma, Zevra Therapeutics (previously KemPharm, Inc), Supernus, Jazz, Corium, LLC, and Lumos. She participated in speaker’s bureau for Takeda (Shire), Arbor, Ironshore, Neos Therapeutics, Tris Pharma, and Supernus; research support from Allergan, Takeda (Shire), Emalex, Akili, Arbor, Ironshore, Lumos, Neos Therapeutics, Otsuka, Purdue, Adlon, Rhodes, Sunovion, Tris Pharma, Zevra Therapeutics (previously KemPharm, Inc), Supernus, US Food and Drug Administration, and Servier. She received writing support from Takeda (Shire), Arbor, Ironshore, Neos Therapeutics, Purdue, Rhodes, Sunovion, and Tris Pharma; and advisory board for Takeda (Shire), Akili, Arbor, Cingulate, Ironshore, Neos Therapeutics, Neurovance, Otsuka, Purdue, Adlon, Rhodes, Sunovion, Tris Pharma, Supernus, NLS Pharma, and Corium, LLC. AJC discloses that in the last 3 years he acted as a consultant for AbbVie, Akili Interactive, Alkermes, Arbor Pharmaceuticals, Axsome, Boehringer Ingelheim, Corium, LLC, Intra-Cellular Therapies, Ironshore Pharmaceuticals, Neurocrine, NeuroSigma, Noven, Otsuka, Purdue Canada, Reviva Pharmaceuticals, Sunovion, Supernus, Shire/Takeda, Teva, and Tris Pharma. He participated in speaker’s bureau for AbbVie, Alkermes, Arbor Pharmaceuticals, Axsome, Corium, LLC, Intra-Cellular Therapies, Ironshore Pharmaceuticals, Neurocrine, Noven, Otsuka, Sunovion, Supernus, Shire/Takeda, Teva, and Tris Pharma. He received research support from AbbVie, Aevi Genomics, Akili Interactive, Alkermes, Allergan, Arbor Pharmaceuticals, Zevra Therapeutics (previously KemPharm, Inc), Ironshore, Otsuka, Purdue Canada, Rhodes, Shire, Sunovion, Supernus, Takeda and Tris Pharma. JE and MC are both employees of Corium, LLC. The authors declare that this study received funding from Zevra Therapeutics (previously KemPharm, Inc) and Corium, LLC. The funders had the following involvement in the study: Zevra Therapeutics was involved in the clinical research, study design, and data collection; Corium LLC was involved in the post hoc analysis and funding the preparation of the manuscript., (Copyright © 2023 Mattingly, Childress, Cutler, Estrada and Corliss.)