Attention-Deficit/Hyperactivity Disorder (ADHD) is characterised by dysregulation in activity levels, attentional control, and impulse control. It emerges during preschool, often persisting into adulthood. Several effective short-term treatments exist, however, improvements are rarely maintained when treatment ceases. Current treatments involve external regulation of symptoms through medication or behaviour management. Our novel early intervention programme addresses the neurocognitive deficits associated with ADHD and teaches preschool children to self-regulate. Results from our open-label trial showed significant reductions in ADHD symptoms and improvements in brain functioning within areas involved in self-regulation. Importantly, improvements in self-regulation were associated with maintained ADHD symptom reduction up to 12-months post-treatment. The proposed randomised control trial will provide a critical test of our programme against treatment as usual (Triple P - parent training).