Aromatic L-amino acid decarboxylase (AADC) deficiency is an inherited disorder that impairs synthesis of dopamine and serotonin. To investigate whether the white matter tracts are impaired in children with AADC deficiency, diffusion tensor imaging data were obtained from 7 children with AADC deficiency and 7 matched controls. Fractional anisotropy (FA) of 76 white matter tracts was measured and compared between the two groups. Fiber tracts of dopaminergic and serotonergic systems, and those connecting regions responsible for executive functions or regulating motor functions showed lower FA in patients. Our findings are consistent with clinical manifestations and pathophysiology of AADC deficiency.