The precise localization of ventricular tachycardia (VT) foci is a prerequisite for the successful radiofrequency catheter ablation in patients. The purpose of this study was to systematically quantify over what distance adjacent sites in the right ventricular (RV) and left ventricular (LV) epicardium and LV endocardium could be distinguished by inspecting morphological features of QRS isointegral maps using statistical methods. We investigated the spatial resolution of QRS isointegral maps by means of an anatomically accurate computer model of the human ventricular myocardium that incorporates a bidomain model for simulating the realistic activation sequences and the oblique dipole model in combination with the boundary element method for calculating extracardiac potentials. In this model, we initiated activation sequences at a total of 183 epicardial and 75 LV endocardial pacing sites, positioned in three levels (basal, middle, and apical). For each of the 258 pacing sites, we calculated a set of 10 QRS isointegral maps with added Gaussian noise at 117 leads (covering the anterior and posterior torso) and at 32 leads (covering only the anterior torso), respectively. Sets of maps were then cross correlated and root-mean-square (RMS) values of difference maps were calculated for all possible pairs of pacing sites on the same level. We applied the nonparametric unpaired Kolmogorov-Smirnov test and defined the spatial resolution as the pacing site separation at which the differences in correlation coefficients and RMS differences were significant (level P < .05). We observed significant differences in maps when the distances between pacing sites were on average (+/- SD) greater than 4.3 +/- 1.0 mm. In more than 90% of pacing sites, the significant differences in maps were observed within 4 mm even when using a 32-lead mapping system. The findings of our study provide theoretical evidence that QRS isointegral maps may offer noninvasive means for preinterventional planning of the ablative treatment in localizing both endocardial and epicardial sites of origin of VT.