Functional magnetic resonance imaging (fMRI) has been shown to be a very useful tool to do research on psychiatric disorders, validating psychotherapeutical interventions, medication as well as disorder-specific deficits. The field of fMRI-research is examining the potential of identifying differences of activity between brains of clinical, subclinical and healthy subjects. The design of such research is drawn to evaluate the average activation to different conditions. We remark that there are still some methodological problems to face, i.e. choosing the sample with special considerations on comorbidity and medication, accounting individual differences in brain activation, complex statistical calculations etc. When evaluating therapeutical interventions it is necessary to take the placebo-effect into account. However, fMRI is a highly promising research method. For future application of fMRI in clinical practice it would be worth building standard paradigms. Then, valid diagnostics of impaired functionality may be possible. Furthermore, fMRI should be combined with other neurodiagnostical technologies and with genetics. The cooperation of different fields in brain research with fMRI may provide further knowledge about psychiatric disorders.