This record contains raw data related to the article "Etiology and Outcome of Catheter Ablation in Patients With Onset of Atrial Fibrillation <45 Years of Age". Abstract Etiologic factors and long-term outcomes of catheter ablation of atrial fibrillation (AF) in young patients have not been well characterized. This study aimed to analyze the etiologic factors and outcomes of pulmonary vein isolation (PVI) in patients with young-onset AF (young-AF, defined as having first documented episode <45 years). Consecutive patients with young-AF undergoing PVI (n = 197) in 2 academic centers were enrolled and followed for 36.1 ± 24.5 months. A control group of patients with AF onset ≥45 years (n = 554) was included. The most frequent risk factors in young-AF were intensive exercise (25%), moderate-to-heavy alcohol consumption (23%), and familial AF (22%). Compared with patients with AF onset ≥45-year, patients with young-AF were more often men (82% vs 66%, p <0.001), had more frequently paroxysmal AF (81% vs 60%, p <0.001), had less left atrial dilatation (40.9 ± 6.2 mm vs 44.2 ± 7.2 mm, p <0.001), and had lower 4-year recurrence rate after last PVI procedure (22% vs 45%, p <0.001). In young-AF, structural heart disease (SHD) was the only independent predictor of recurrence. Patients with young-AF selected to undergo cryoballoon (CB) ablation were younger (35.0 ± 7.7 vs 36.6 ± 6.7 years, p = 0.035) and had less persistent AF (6% vs 24%, p = 0.004) and coronary artery disease (2% vs 7%, p = 0.02) compared with radiofrequency ablation. After excluding patients with persistent AF and SHD, there was no difference in single procedural success between radiofrequency or CB PVI (27% vs 17%, p = 0.11). In conclusion, patients with young-AF have diverse etiologies and high single and multiprocedural PVI successes. SHD is the only independent predictor of recurrence. In patients with young-AF, there is a selection bias for CB ablation.