Background: The degree of left atrial (LA) voltage may reflect the severity of tissue pathology underlying atrial fibrillation (AF) and may predict treatment outcome. In patients with persistent AF, however, LA voltage mapping is not always feasible because of difficulty in maintaining sinus rhythm (SR) even after repeated electrical cardioversions. The purpose of this study was to compare LA voltage map obtained from automated 3-D map of complex fractionated electrogram (CFE) with LA voltage map during SR. Methods and Results: A total of 20 patients with persistent AF for whom both the CFE and the LA voltage map were available were enrolled. After obtaining CFE map utilizing an electroanatomic mapping system (NavX), modified LA voltage map was created by manually with selection of absolute peak amplitude for 6-second recordings of bipolar electrograms. A conventional LA voltage map was obtained during SR after electrical cardioversion. Compared with conventional method, LA voltage obtained from 3-D CFE map was significantly lower (1.86짹0.82 mV vs. 0.83짹0.46 mV, P<0.001), but significantly correlated with that from conventional method (r=0.728, P<0.001). Scar zones (<0.2 mV) in 3-D CFE map appears to be the same sites as low voltage (<0.5 mV) or scar zones in conventional method (positive predictive value 76.7%, negative predictive value 95.2%). Conclusion: Although 3-D CFE map during AF underestimates LA voltage by approximately 64% (coefficient rate), LA voltage determined by peak amplitude during AF was closely correlated with true LA voltage during SR. Assessment of LA voltage by 3-D CFE map was feasible and alternative method in patients with persistent AF who required frequent electrical cardioversion to maintain SR.