Atrial fibrillation ablation is a complex and challenging procedure. Appropriate patient selection is the most critical step to ensure safe and successful atrial fibrillation ablation procedure. The DECAAF study (Delayed-Enhancement MRI Determinant of Successful Radiofrequency Catheter Ablation of Atrial Fibrillation) showed that atrial tissue fibrosis, as estimated by delayed enhancement magnetic resonance imaging, was independently associated with recurrent arrhythmia post atrial fibrillation ablation. Magnetic resonance imaging also detected left atrial volume and shape. Integrating the data provided by magnetic resonance imaging into the pre-procedural planning is crucial.