Magnetic Nuclear Resonance (MRI) is a non-invasive tissue imaging method. This technique is based on the influence of a strong magnetic field and electromagnetic wave of strictly defined frequency on the nucleus of elements with non-zero spin. The study describes one of the variants of functional MRI, (fMRI), which has become a key technique in brain imaging. This technique has excellent spatial and temporal resolution and involves a changing signal intensity depending on the degree of oxygenation of the blood. Blood oxygenation levels are known to vary in accordance with neural activity and these differences can be used to detect brain activity. This is due to increased demand for energy and oxygen in the area of increased neural activity. The basis of this imaging is the so-called Blood Oxygenation-Level Dependent (BLOD) effect. The aim of this paper is to present the scope of fMRI as a diagnostic method in neurology and in neurosurgery. This paper presents the principles of fMRI, methods of application, research result development, and suggests areas of possible medical applications. The limitations of fMRI as a clinical tool in medical applications will also be addressed. Studies presented in this paper are based on clinical fMRI experience and a literature review.