Diffusion tensor imaging (DTI) studies examining white matter microstructure in children with attention-deficit/hyperactivity disorder (ADHD) have provided conflicting results, possibly reflecting limitations of the DTI framework. We leverage fixel-based analysis (FBA), a fibre specific assessment of white matter microstructure, to comprehensively evaluate white matter tract profiles of children with ADHD. Relative to controls, children with ADHD show both reduced fibre density and reduced fibre cross section across association, projection and commissural fibres. FBA metrics further correlate with ADHD symptom severity. We conclude that ADHD symptomatology in childhood may be subserved by altered communication pathways across the brain.