Recent insights suggest an etiological contribution of sleep disorders in sub-groups of ADHD patients, specifically sleep-onset insomnia. Chronobiological treatments, such as melatonin and morning bright light, have demonstrated clinical effects in ADHD. We recently demonstrated an association between the worldwide prevalence of ADHD and solar intensity as a further indication of the role of circadian dysregulation and sleep in the etiology of ADHD. In relation to neurofeedback, it has been demonstrated that Sensori-Motor Rhythm (SMR) neurofeedback impacts the sleep spindle circuitry (SSC) resulting in increased sleep-spindle density. Overlap between the reticulo-thalamo-cortical SSC and the circadian network has been reported, suggesting overlap between neurofeedback and chronobiological treatments. The treatment effects on ADHD symptoms, such as inattention, hyperactivity, and impulsivity, thus arise as a result of normalized sleep. This will be demonstrated based on a recent study, where only for SMR neurofeedback it was found that improvement in sleep onset latency mediated the improvements on inattention. For Theta/Beta neurofeedback this was not found, suggesting specificity of SMR and Theta/Beta neurofeedback protocols in the treatment of ADHD.