To evaluate the modification of hemodynamic parameters and of synchrony using radionuclide angiography (RNA), as well as the effect on myocardial perfusion, 20 patients with dilated cardiomyopathy (DCM) were studied before and five months after cardiac resynchronization therapy (CRT),. Inter-and intraventricular synchronization was assessed by phase analysis. After CRT, left ventricular ejection fraction improved from 22 ± 5% to 29 ± 13%, p=0.04. There was a significant reduction of intraventricular asynchrony in ischemic patients. There was no difference between inter-and intraventricular asynchrony measured by RNA and echocardiography at baseline nor for the improvement after CRT. The summed rest score (SRS) decreased from 33±14 to 21±12 (p=0.004). SRS reduced from 35±12 to 27±9 (p NS) among ischemic patients, and from 31±17 to 17±11 (p=0.02) among non-ischemic. Radionuclide angiography is a useful method to assess heart failure patients before and after CRT. CRT improves myocardial perfusion mainly in non-ischemic patients.