Cardiac masses are usually first detected at echocardiography. In their further evaluation, cardiac magnetic resonance (MR) imaging has become a highly valuable technique. MR imaging offers incremental value owing to its larger field of view, superior tissue contrast, versatility in image planes, and unique ability to enable discrimination of different tissue characteristics, such as water and fat content, which give rise to particular signal patterns with T1- and T2-weighted techniques. With contrast material-enhanced MR imaging, additional tissue properties such as vascularity and fibrosis can be demonstrated. MR imaging can therefore contribute to the diagnosis of a cardiac mass as well as be used to detail its relationship to other cardiac and extracardiac structures. These assessments are important to plan therapy, such as surgical intervention. In addition, serial MR studies can be used to monitor tumor regression after surgery or chemotherapy. Primary cardiac tumors are very rare; metastases and pseudotumors (eg, thrombus) are much more common. This article provides an overview of cardiac masses and reviews the optimal MR imaging techniques for their assessment. © RSNA, 2013 Supplemental material:http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13121239/-/DC1.