Diffusion tensor imaging (DTI) is an MRI technique using which we can study the orientation and integrity of white matter tracts in vivo by measuring the diffusion of water in neural tissue. Within white matter, structure such as axonal membranes, myelin sheaths, and neurofibrils (microtubules, neurofilaments) could potentially restrict perpendicular water diffusion and generate anisotropy. By means of anisotropy quantification, e.g. fractional anisotropy (FA) or relative anisotropy (RA) we can provide information about the preferred direction of diffusion and major fibers integrity. Thus, with this method we can investigate white matter damages as well as provide information about structural connectivity among brain regions. Driven by the main hypothesis of a disturbed structural and functional interplay of certain brain regions in patients with schizophrenia, affective disorders as well as with obsessive-compulsive disorder, the research focus of our group is to combine DTI parameters with parameters of functional and effective connectivity extracted from the fMRI experiments. To make statistical comparisons we employ voxel-based analysis (VBA), tract-based spatial statistics (TBSS) and tractography methods using fMRI activation cluster as seed regions.