Background: Catheter ablation puts cardiac valves at risk of damage, and children are of particular concern. Methods: A multicenter prospective study was performed to assess the results and risks associated with radiofrequency (RF) ablation in children. Patients were aged 0 to 16 years with supraventricular tachycardia due to accessory pathway or atrioventricular node reentry, excluding patients with more than trivial congenital heart disease. A total of 481 patients were recruited into the prospective cohort and were followed up at 2, 6 and, 12 months after ablation. Complete echocardiograms were obtained before and at intervals after RF ablation, and they were reviewed by experts who were blinded with respect to diagnosis, outcome, pathway site, and study interval. Results: Moderate valve insufficiency was quite rare (0.12%), but mild insufficiency was common, both before ablation (42.43%) and at 2 months after ablation (40.49%). Analysis of paired readings failed to demonstrate a tendency toward increased insufficiency of valves adjacent to ablation targets, with the exception of the tricuspid valve after the ablation of right freewall pathways and atrioventricular node reentry, but the degree of change was small. No clear changes in left ventricular systolic or diastolic function were observed, and dyskinesis was rare and not related to the ablation target. No intracardiac thrombosis was observed. Conclusions: Serious injury to cardiac valves due to RF ablation is very rare, but the tricuspid valve may be mildly affected in some cases. We identified no clear effect of RF ablation on cardiac wall motion or on left ventricular function.