Objective: The purpose of this study is to compare the role of magnetic resonance imaging (MRI) with transthoracic echocardiography (TTE) for characterization of cardiac masses. Methods: Twenty-three patients were examined with a 1.5T MRI Scanner and TTE for the evaluation of suspected intracardiac masses. MRI examinations were performed with a protocol of steady cine imaging, HASTE and 3D IR-FLASH sequence after administration of gadolinium chelate. All patients were examined with MRI within a period of 1-2 weeks after TTE. Results: According to the results of MRI, 15 patients underwent cardiac surgery. All of the operated patients were proven to have cardiac tumors with no false positive diagnosis on MRI. In 3 of 8 unoperated patients who were diagnosed to have cardiac tumors on TTE, cardiac thrombi were identified on MRI. Two patients with Eustachian valve in the right atrium on MRI were misinterpreted as having cardiac masses on TTE. In one patient with known renal cancer, metastases were diagnosed within the myocardium on MRI. TTE demonstrated a mass in the left atrium in one patient with a history of myxoma operation, whereas MRI was able to show the paracardiac extension of the mass into pulmonary veins and lung metastases, which are indicators of malignant transformation. In one patient, a mediastinal mass compressing the left atrium on MRI was misinterpreted as an intracavitary lesion with TTE. Conclusion: Contrast enhanced MRI is a noninvasive method superior to TTE in diagnosis, differentiation, and detection of extension of cardiac masses.