Background Recent investigations demonstrated that obstructive sleep apnea (OSA) is an important precipitating factor of atrial fibrillation (AF).This study attempts to determine whether OSA can affect success rate of biatrial ablation in patients with persistent AF. Method Fifty-six patients with longstanding persistent atrial fibrillation (LPAF, AF episode > 1 year) (Mean age 57짹9.9) had undergone radiofrequency catheter ablation (RFCA) including pulmonary vein isolation +automated 3-D complex fractionated atrial electrogram (CFAE) guided ablation at both atria.OSA was assessed by the Berlin Questionnaire (BQ). The primary endpoints during RF ablation were defined as complete elimination of the areas with CFAEs and conversion of AF to sinus rhythm. Echocardiographic parameters including pulmonary artery pressure, left atrial volume were evaluated. Result Compared to patients with LPAF termination by biatrial ablation, patients who did not terminate AF(n=28, 50%) had a higher pulmonary pressure [33.1짹6.4 mmHg vs. 29.0짹3.5 mmHg, p=0.012) and greater number of the patients for high risk of OSA (n=17, 73.3%, vs. n=11, 41.5%, p = 0.032]] Univariate analysis revealed that age (OR 0.94, CI: 0.88–0.99, p= 0.038), pulmonary arterial pressure (OR 1.19, CI: 1.02–1.38, p= 0.023) and high risk for OSA (OR 3.38, CI: 1.06–14.3, p= 0.04) were related with failure of biatrial ablation. On multivariate analysis, age (OR 0.842, CI: 0.74–0.96, p= 0.01) and high risk for OSA (OR 11.9, CI: 1.1–129.2, p= 0.04) were independent predictors for RFCA failure. Conclusion High risk for OSA predicts RFCA failure after extensive biatrial ablation in patients with LPAF.