AIM It has been demonstrated that atrial fibrillation (AF) frequently recurred after cardioversion (CV) using direct current (DC) or radiofrequency catheter ablation (RFCA) in patients with persistent (PeAF) or longstanding persistent AF (LPAF). We hypothesized that the atrial substrate impeding successful CV would also produce difficulty in catheter ablation, and therefore, the outcomes of RFCA for PeAF and LPAF could be predicted by the parameters determined at the time of DC CV. METHOD From 2006 to 2009, 94 patients with PeAF and LPAF who had undergone elective DC CV before RFCA were studied. The parameters associated with DC CV, including number of shocks, cumulative energy adjusted, highest energy adjusted, with or without intravenous amiodarone use, and other clinical parameters were assessed. RESULT Thirty-two out of the 94 patients (34%) experienced AF recurrence during the follow-up of 19.8 ± 12.3 months after RFCA. The average time to recurrence of AF after RFCA was 9.2 ± 3.2 months. Of the 62 patients, 29 patients (31%) remained sinus rhythm (SR) without antiarrhythmic drug (AAD). The patients who maintained SR had smaller body mass index (BMI) (P = 0.048), shorter duration of AF (P = 0.012), and lower prevalence of diabetes mellitus (P = 0.023) compared with patients in whom AF recurred. Total number of shocks, total energy, and highest shock energy during CV were lower (P < 0.001, P = 0.002, P = 0.048, respectively) in patients with SR during the follow-up. The outcome in patients who used amiodarone IV prior to CV, however, was not different from that in those who did not use amiodarone IV. CONCLUSION DC energy parameters for successful CV before RFCA were useful to predict the long-term outcome after RFCA in patients with PeAF and LPAF. The presence of the atrial substrate making DC CV difficult might reflect atrial substrate that subsequently related to the recurrence of AF after RFCA in chronic AF. These DC energy parameters may be related to the chronicity or electroanatomical remodeling of AF.