123I-Iodine-metaiodobenzylguanidine(MIBG) which is a norepinephrine analogue, can be used to evaluate the sympathetic innervation of the heart. In this study, cardiac imaging with 123I-MIBG was performed in patients with 9 dilated cardiomyopathy, 2 ischemic cardiomyopathy and 1 acute myocardial infarction to evaluate the sympathetic nervous function. 123II-MIBG imaging showed multifocal defects (8), diffuse defect (2), near non-visualization (2). The defects of MIBG scans were found to be larger and more severe on 4 hours image than 30 minutes. Heart to lung, heart to mediastinum ratios were decreased at 4 hours than those at 30 minutes. Measured LVEF values were not correlated with the severity of MIBG uptake. Tc-99m-MIBI imaging was also performed in all patients to find the relationship with 123I-MIBG scan. Tc-99m-MIBI scan showed multifocal defects in 9 patients, diffuse defects in 1 patient and no defect in 2 patients. The defects are similar in size, severity and extent, but more larger and severe on 123I-MIBG imaging. Therefore, cardiac 123I-MIBG imaging is a useful method to evaluate the sympathetic nervous function in cardiomyopathy.