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Background: Recent studies have linked exposure to airborne particulate matter (PM) to neurodevelopmental outcomes but the findings are mixed and mechanisms are unclear. We aim to determine the impact of PM on the developing brain of schoolchildren in Poland, a European country characterized by very high levels of air pollution. Methods: During 2020-2021, 800 children aged 10 to 13 years will be recruited in a case-control study. Attention Deficit Hyperactivity Disorder (ADHD) cases will be sampled from psychological centres and clinics. Population-based controls will be sampled from schools. The study area will include 20 towns in southern Poland characterized by different PM levels. Behavioural testing will be done using a battery of tests, including the inhibition measuring Go-NoGo task and the Attention Network Task. Magnetic Resonance Imaging (MRI) acquisition will be conducted in line with the Human Connectome Project Adolescent Brain Cognitive Development protocols (resting-state functional MRI, Diffusion Tensor Imaging (DTI), T1/T2 structural MRI, one functional MRI task - Conditioned Approach Response Inhibition Task (CARIT)). Estimates of PM and other air pollutants will be modelled using a combination of land use regression, transport models, satellite observations and monitoring data. These will be assigned to prenatal and early postnatal residential addresses of children. Associations of PM with ADHD-related symptoms, intelligence quotient (IQ), attention, emotional and social function and the role of changes in specific brain regions will be assessed by mediation models, adjusted for confounders. Results and Discussion: This comprehensive four-year study will provide novel, in-depth understanding of the neurodevelopmental effects of PM.