Inclusion Criteria:  children aged 4-6 years old with psychiatrist or psychologist diagnosis of ADHD according to the DSM-5 manual or other clinical diagnosis criteria; or as indicated by the ratings of Swanson, Nolan and Pelham Parent Rating Scale (SNAP-IV; Chinese version); with normal IQ (above 80), which enable them to understand the materials delivered in the training program; children either not taking any medication or taking a stable dosage of medication for ADHD for at least 3 months prior to the study enrollment and will not be taking the medication during the training and post-assessment period.  Exclusion Criteria:  inability to comprehend Cantonese, with comorbid disorders (i.e. autism, conduct/behavioural problems), with medical or other mental health condition with IQ below 80 with physical and motor disabilities that restrain them from completing the tasks.