Structural and functional neuroimaging research into ADHD has generated overwhelming and compelling evidence that ADHD symptoms are a manifestation of abnormally functioning brain circuitry [4, 38, 156, 260, 266, 278, 279]. Brain volume abnormalities are consistently found in the cerebellum, the corpus callosum splenium, total and right cerebral hemisphere volume, and within the right caudate nucleus of people with ADHD [280]. Brain structure deficits have been found in gray and white matter volume of subjects with ADHD [43, 280–282]. Differences in cortical thickness have been identified in ADHD populations versus normal controls, and differences in white matter microstructure measured through diffusion tensor imaging have been identified [283, 284]. Functional brain abnormalities in prefrontal–striatal–cerebellar brain regions have also been observed [4, 42, 202, 285].