DTI images illustrating the eight White Matter (WM) tracts measured in this study. Anterior corona radiata (ACR) - WM tract extending from dorsolateral and ventrolateral prefrontal cortex primarily to pretectum. WM fibers of the internal capsule including: Anterior limb of the internal capsule (ALIC), Superior region of the internal capsule (SRI) and Posterior limb of the internal capsule (PLIC); Superior longitudinal fasciculus II (SLF II) which connects the PFC and the caudal inferior parietal lobule; Inferior longitudinal fasciculus (ILF) comprised of U-shaped fibers connecting extrastriate visual association areas and temporal regions involved in transfering visual signals to anterior temporal regions and also including projections from amygdala to early visual areas; Cingulum bundle (CG) that includes WM fibers that connect to prefrontal cortex, anterior cingulate cortex, thalamus and somatosensory regions; Splenium (SP) including posterior bulb of the corpus callosum that joins the posterior cortical regions across the cerebral hemispheres. For all regions, with the exception of SP, the ADHD group exhibited significantly greater values than the other two groups, which did not differ from each other. For SP only, the ADHD and PBD groups did not differ from each other, and exhibited greater values than HC. *p<0.001; **p<0.001.