In patients with structural heart disease (SHD), defined by the presence of myocardial scarring either on cardiac imaging or electroanatomical mapping, catheter ablation is increasingly used for the treatment of ventricular tachycardia (VT). With more detailed knowledge of potential substrates and anatomic structures involved in VT, not only the endocardium of the left ventricle (LV) and right ventricle (RV) but also more complex structures like the aortic root, the cardiac veins, or the epicardium have become areas of interest for ablation. Preprocedural analysis of the clinically documented VT 12-lead ECG is often used to predict the VT site of origin (SoO), and it is considered to be an important tool for planning the ablation, to estimate the probability of success, and to recognize potential procedural limitations and related risks. These factors may have important implications not only for patient advice and decision making but also for the selection of a center capable to perform the expected procedure. Because the majority of inducible VTs in patients with SHD are not hemodynamically tolerated,1,2 a detailed analysis of the VT 12-lead ECG of each induced VT may also be helpful. Combining the ECG with information of the scar size and distribution obtained from electroanatomical mapping during sinus rhythm or from preprocedural imaging may direct mapping to the area of interest with the potential of increasing procedural success and to reduce procedural duration. In this review, we will focus on the reported evidence for the value of the 12-lead VT ECG as a mapping tool in patients with scar-related VT and discuss its potential implications when combined with scar information from electroanatomical mapping or imaging. The mechanism of the majority of VTs in patients with structurally normal hearts is focal, and the 12-lead ECG can be helpful to predict its SoO …