Background: In patients with ventricular tachycardia (VT) originating from the right ventricular outflow tract (RVOT), a limited study showed no abnormal voltage regions in the RVOT using electroanatomical mapping during sinus rhythm. We evaluated the electroanatomic substrate of RVOT VT. Methods: We enrolled eleven patients who underwent catheter ablation using electroanatomical mapping of typical RVOT VT. Detailed RV electroanatomical maps focused on the RVOT, were generated during ventricular premature contractions (VPCs) with the same morphology as the VT. We ablated the VT at the earliest point in the electroanatomical map, and analyzed the bipolar voltage maps of the RVOT and the relationship between the successful site and abnormal voltage areas. Abnormal voltage and dense scar area were defined as having a voltage of less than 1.5mV and 0.5mV respectively. Results: The area of abnormal voltage and dense scar regions in the RVOT were 8.83짹4.9��� and 5.49짹2.8���, respectively. The voltage amplitude and duration of the bipolar electrograms at successful sites were 2.14짹2.2mV and 95.91짹36.0ms, respectively. The percentage of an abnormal voltage at the successful site was 63.6%. We could ablate the focus successfully in all patients and those sites were 30.27짹14.6ms earlier than the VPC onset. The distance between ablation site and border of abnormal voltage and normal voltage was 4.82짹5.89mm. In 9 patients (81.8%), the ablation site was located within 6mm of the border. Conclusion: Electroanatomical mapping of the RVOT demonstrated a small-sized abnormal voltage area in all study patients with RVOT VT. The VT site of origin corresponded to the border of the low voltage zone. Electroanatomical substrate mapping may be helpful in ablating RVOT VT.