Neurosurgery in functionally relevant brain structures carries a high risk for surgery induced post-operative neurological deficits. Functional magnetic resonance imaging (fMRI) is one of the most commonly used functional neuroimaging techniques for pre-surgical brain mapping. Preoperative fMRI is optimal method to localize specific functions of the human brain that govern motor, sensory or language functions. fMRI facilitates the selection of the safest treatment and is very helpful to plane and to perform function preserving surgery in patients with brain tumors. This kind of examination is feasible for clinical routine neuroimaging and provides important diagnostic information noninvasively that is otherwise unavailable. fMRI examinations require also advanced software for data analysis.