Background: The Belgian ‘National Institute for Health and Disability Insurance (RIZIV-INAMI)’ requested prospective collection of data on all ablations in Belgium to determine the outcomes of surgical ablation of atrial fibrillation (AF) during concomitant cardiac surgery. Methods: 890 patients undergoing concomitant ablation for AF between 2011 and 2016 were prospectively followed. Freedom from AF with and without anti-arrhythmic drugs was calculated for 817 patients with follow-up beyond the 3-month blanking period and for 574 patients with sufficient rhythm-related follow-up consisting of at least one Holter registration or a skipped Holter due to AF being evident on ECG. Besides preoperative AF type, concomitant procedure and ablation, potential covariates were entered into uni- and multivariable regression models to determine predictors of outcome. Results: The overall freedom from AF beyond 3 months was 69.9% (571/817) and without anti-arrhythmic drugs at last follow-up 51.0% (417/817), respectively, ...