Attention deficit hyperactivity disorder (ADHD) is one of the most prevalent neurodevelopmental disorders, characterised by inattention, hyperactivity, and impulsivity. Although pharmacotherapy is considered the first-line treatment for ADHD at all ages (at least for severe cases), non-pharmacological therapies might be equally effective without the risk of drug side effects. Some studies have shown that electroencephalographic (EEG) neurofeedback improves parent-rated ADHD symptoms in children and adolescents. However, whether neurofeedback is an effective treatment for ADHD is still under debate. Several issues may hinder the evaluation of the effectiveness of neurofeedback treatment in previous studies. Firstly, previous neurofeedback studies did not utilize effective neurophysiological markers for ADHD. Theta/Beta ratio, the most common neurofeedback marker for treating ADHD in the past two decades, has recently been suggested to be only weakly correlated to individuals' attention. Secondly, previous studies mostly used the norm of the EEG markers in age/gender matched healthy children as the training target for ADHD children, which largely ignored the individual variations in EEG acquisition. Third, most of the previous studies lack a rigorous study design, for comparing neurofeedback with a 'placebo' condition and evaluating its specific and non-specific effects. In the current studies, we propose to conduct a sham-controlled, triple-blind trial to evaluate the effectiveness of an individual-based neurofeedback treatment for ADHD children and adolescents. The EEG marker for neurofeedback in treating ADHD would be the individualized lower/higher alpha band power, based on the recent methodological advances in EEG spectrum processing (1/f model fit and individualized peak alpha frequency modelling) . The training target will be individualized and defined according to the neurophysiological pattern shown in pre-training resting-state conditions, and thus each participant will be trained to achieve their own optimum state of engagement. Sham neurofeedback will be used as a placebo condition, controlling for the non-specific effect of neurofeedback. The study will be triple-blinded (i.e, participants, individuals who administered treatment or intervention, and those who assessed the outcomes were masked).