Experience-based neuroplasticity has typically been associated with functional changes, but growing evidence indicates that training can also render dynamic structural alterations in the brain. Although research on training-induced morphological plasticity has consistently demonstrated rapid increases of gray matter volume in task-related regions, no studies have examined if local volumetric reductions in gray matter associated with certain psychiatric disorders may be reversible by adequate training. We aimed to assess whether a training program applied to ADHD patients can contravene some of the associated neuroanatomical alterations. High-resolution anatomical scans were acquired before and after the training period, and a whole-brain tensor-based morphometric approach was applied to extract a voxel-wise estimation of longitudinal changes in regional gray matter volume. Our results show focal volumetric gray matter increases in bilateral middle frontal cortex and right inferior–posterior cerebellum after cognitive training compared with the ADHD control group. The extent of gray matter volume increase in the inferior–posterior cerebellum was associated with attentional performance. These findings illustrate the capacity of the nervous system for rapid morphological adjustments in response to environmental triggers. Moreover, the dorsolateral prefrontal cortex and cerebellum are commonly considered sites of volumetric reduction in ADHD, and the inferior–posterior lobule of the cerebellum is associated with progressive symptom-related volume loss. Hence, the clusters of volumetric change observed in our study were confined to structures typically characterized by volume reduction in ADHD patients, providing preliminary indications that cognitive training may contravene some of the neuroanatomical deficits associated with the disorder. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc.