Background: Some of atrial fibrillation (AF) drivers are found in lesser late-gadolinium enhancement (LGE) areas, as well as heterogenous ones. The atrial wall thickness (AWT) has been reported to be important as a possible AF substrate. However, the AWT and degree of LGEs as an AF substrate has not been fully validated in humans. Objective: The purpose of this study was to evaluate the impact of the AWT in lesser LGE areas on AF drivers. Methods: A total of 287 segments in 15 persistent AF patients were assessed. AF drivers were defined as non-passively activated areas (NPAs), where rotational activation was frequently observed, and were detected by the novel real-time phase mapping (ExTRa Mapping). Lesser LGE areas were defined as areas with a volume ratio of the enhancement voxel of <10%. The AWT was defined as the minimum distance from the manually determined endocardium to the epicardial border on the LGE-MRI. Results: NPAs were found in 20 (18.0%) of 131 lesser LGE areas where the AWT was significantly thicker than that in the passively activated areas (PAs) (2.46±0.26 vs. 2.20±0.25 mm, p<0.001). However, NPAs were found in 61 (21.3%) of 287 LGE areas where the AWT was similar to that of the PAs (2.24±0.24 vs. 2.22±0.25 mm, p=0.58). An ROC curve analysis yielded an optimal cutoff value of 2.24 mm for predicting the presence of an NPA in lesser LGE areas. Conclusion: The location of AF drivers in lesser LGE areas might be more accurately identified by evaluating the AWT.