Background Although there have been several reports for electrocardiographic (ECG) analyses of ventricular arrhythmias originated from left ventricular outflow tract (LVOT), those were dependant on the mapping area of interests. We simultaneously mapped aortic cusp (AC), anterior interventricular vein (AIV), and anterior mitral annulus (AMA), and matched the successful ablation sites with ECG findings. Methods and Results Twenty five patients (Female 13, mean age 47짹12 years) with ventricular tachycardia (VT) or frequent premature ventricular contractions (PVC) originated from AC, AIV, or AMA were mapped and ablated. If the endocardial radiofrequency catheter ablation (RFCA) was not successful, anterior interventricular epicardium (AIE) was mapped by subxiphoid percutaneous pericardial approach. ECG findings were compared with the successful ablation site. Results: 1. Successful ablation sites were left coronary cusp (LCC) in 12 patients (9 above valve), AIE in 6 (1 inside AIV), right CC (RCC) in 5 (4 above valve), and AMA in 2 patients. 2. RCC-VT showed positive lead I, negative V1, and shorter QRS width (p<0.001) than other 3 groups. 3. LCC-VT could not be differentiated from AIE-VT by QRS polarity alone, but multiple QRS morphologies (2/12 vs. 3/6) and double precordial transitions in V1-3 (2/12 vs. 5/6) were less common in LCC-VT than in AIE-VT. QRS width (p<0.05) was rather longer in LCC-VT than in AIE-VT. 4. AMA-VT showed longer QRS width (p<0.001) and intrinsicoid deflection time in V2 (p<0.01) than LCC or AIE-VT. 5. The mean number of RF delivery was higher in AIE-VT (12짹7) than in AC or AMA-VT (2.2짹1.4, p<0.001). At 13.3짹6.9 months of follow-up, one patient in LCC who was treated by low power of ablation (20W, 50C) and 3/6 AIE-VT recurred PVC. Conclusion Although there are characteristic ECG morphologies in each LVOT origin of ventricular arrhythmias, their distinct localization by surface ECG is limited and overlapped. Therefore, detailed mapping above AC (13/25) has to be firstly considered prior to the mapping of the exits at the adjacent areas.