The purpose of this article is to review the characteristics of computed tomography (CT) and magnetic resonance imaging (MRI) of the pericardium and pericardial diseases. Because patients with pericardial diseases usually present with nonspecific symptoms, these diseases may not be detected until they have reached an advanced stage. It is therefore important to distinguish between normal pericardial structure and disease. Multiplanar reconstruction images of CT and MRI are useful for evaluating faint changes of the pericardium. The specific pericardial diseases described in this article include pericardial cyst, constrictive pericarditis, pericarditis with radiation pericarditis, postoperative pericardial hematoma, and cardiac tamponade due to a paracardiac mass (lymphoma).