Background: There is a paucity of information concerning left ventricular (LV) dyssynchrony assessment by real time three‐dimensional (3D) echocardiography (RT3DE) versus tissue Doppler imaging (TDI). Aims: To compare RT3DE and TDI LV dyssynchrony assessment. Methods: A prospective study of 92 individuals (56 men, age 47 ± 10 years), 32 with dilated cardiomyopathy (CMP), and 60 healthy individuals. By RT3DE, we measured the LV% dyssynchrony index (DI) of 6, 12, and 16 segments (SDI). By pulsed‐wave TDI, we measured the QS electromechanical interval in the basal segments of the mitral valve annulus of the septum, the lateral, anterior and inferior walls, and the TDI% DI. Results: In the normal group, the 3D DI was 1.1 ± 0.8%, 1.4 ± 1.3%, 1.8 ± 1.7%, for 6 segments, 12 segments, and SDI, respectively. The correlation coefficient (Pearson's r) for the TDI DI and SDI was r = 0.2381 (P = 0.0470). In CMP group, the 3D DI was 4.6 ± 5.4%, 7.9 ± 7.1%, 11.1 ± 7.1%, for 6 segments, 12 segments, and SDI, respectively. The correlation coefficient for TDI DI and SDI was r = 0.7838 (P < 0.0001). Conclusions: We observed a good correlation between RT3DE and tissue Doppler LV dyssynchrony assessment in patients with advanced heart failure. (ECHOCARDIOGRAPHY, Volume 26, July 2009)