The Susceptibility-weighted (SWI) imaging is a recent MRI sequence that shows the magnetic susceptibility differences of various tissues. A large number of neurological / neurosurgical diseases can benefit with this MRI sequence. The basic physics principles are reviewed and also its clinical application in several brain pathologies in adults and in paediatrics, mainly vascular, tumors and neurodegenerative/genetic disorders. Some clinical cases show the utility of SWI. The anatomic detail of some brain structures, the deep venous system and mesencephalic structures is shown.