Magnetic Resonance imaging (MRi) is a new imaging technique. The authors review the basic principles and present several cases comparing MRi with CT scanning and surgical findings. The major advantages of MRi include lack of ionizing radiation, non-invasiveness and absence of interpetrous artifact when visualizing the posterior fossa. Magnetic Resonance imaging of the posterior fossa, especially of the brain stem and cranial junction, has significant advantages over imaging by CT scanning.