The relationship between attention-deficit/hyperactivity disorder (ADHD) and sleep is complex and poses many challenges in clinical practice. Recent studies have helped to elucidate the nature of the neuromodulator systems underlying the associations among sleepiness, arousal, and attention. Studies of sleep disturbances in children with academic and behavioral problems have also underscored the role that primary sleep disorders play in the clinical presentation of symptoms of inattention and behavioral dysregulation. Recent research has shed further light on the prevalence, type, risk factors for, and impact of sleep disturbances on children with ADHD. The following discussion of the multilevel and bidirectional relationships among sleep, neurobehavioral functioning, and the clinical syndrome of ADHD synthesizes current knowledge about the interaction of sleep and attention/arousal in these children. Guidelines are provided to outline a clinical approach to evaluating and managing children with ADHD and sleep problems.