Background: Attention and executive function (EF) deficits in children negatively impact academics, social interactions, and overall quality of life. Children with other brain-based disorders are at high risk for attention and EF concerns, but the effects of these impairments are not well studied in the literature. The Complex Attention and Executive Function Clinic at the Alberta Children’s Hospital collected baseline data on patients referred for concerns of attention deficits co-occurring with diagnosed neurologic illness/injury, or neurodevelopmental disorder (NDD). Methods: The Behaviour Rating Inventory of Executive Function (BRIEF-2), Behaviour Assessment System for Children (BASC-3), Parenting Stress Index (PSI-4) and medical and past treatment information were collected on initial clinic visit for patients aged 5-15 years. Results: BRIEF-2 Global Executive Composite demonstrated 88.9% of children had clinically elevated scores. Clinically significant scores were observed in 55.5% for BASC-3 Adaptive Skills index and 40% of parents in PSI-4 Total Stress scores. Conclusions: Children with neurologic illness/NDDs are at high risk of clinical impairments in attention and EF. In children referred for attention and behavioural regulation, there is clinically significant increased reporting of executive function impairment out of proportion to other behavioural difficulties. The clinic aims to improve overall functioning through treatment of unmanaged attention and EF deficits.