Diffusion tensor MR imaging (DTI) can provide in vivo unique information on integrity of white matter structures (anisotropy) and connectivity (fiber tracking) in the human brain. This is made possible by means of non-invasive MR-based technique. The purpose of this article is to review the method and the current applications of diffusion tensor MR imaging. Studies of the past decade featuring relevant neuropsychiatric disorders as well as disorders in child psychiatry are reviewed. Furthermore, this report offers a summary of DTI-studies in children and adolescents showing alterations in brain or CNS structures including neurological, traumatological and oncological investigations. In particular, it focuses on the importance of this method with respect to exploration of normal and pathological brain development.