Cardiac magnetic resonance (CMR) imaging has progressively become part of the imaging methods recommended in patients with heart failure. CMR represents the gold standard for assessing volumes, function, biventricular kinetics and providing tissue characterization through scans with and without contrast medium. In patients with heart failure with reduced ejection fraction (HFrEF) and ischemic dilated cardiomyopathy, CMR allows to search for viability, accurately estimate volumes and ejection fraction. It can assess scar extent for predicting response to cardiac resynchronization therapy and for establishing an indication for implanting a defibrillator in borderline cases. In patients with HFrEF and non-ischemic dilated cardiomyopathy, CMR helps to identify specific etiological subgroups and to estimate the arrhythmic risk beyond ejection fraction. In patients with heart failure with preserved ejection fraction, CMR offers the possibility of diagnosing specific phenotypes, including sarcomeric hypertrophic cardiomyopathy, amyloidosis or Fabry disease, and adds prognostic information. Both clinical and scientific interest in this imaging method is constantly expanding; the clinicians dealing with heart failure cannot fail to know the technique, the indications and all the potential that CMR can offer.