Cardiomyopathies are a group of diseases that are associated with myocardial dysfunction and/or arrhythmia due to abnormalities of the myocardium. Echocardiography is the most commonly used method for functional evaluation and classification of cardiomyopathy since it is widely available. Magnetic resonance imaging (MRI) has recently emerged as a well-validated diagnostic tool for the understanding and treatment of these conditions. Morphological and functional information can be achieved with a high level of accuracy and reproducibility. This article reviews the applications of MRI in relationship to echocardiography for the diagnosis of cardiomyopathy and arrhythmogenic conditions of the heart.