For most cardiac arrhythmias, antiarrhythmic drug therapy has only modest effectiveness. In addition to that, antiarrhythmic drugs have numerous side effects, proarrhythmic effects and they have very high cost in the long term. In the last two decades invasive electrophysiology (EP) and radiofrequency or cryo catheter ablation have become common and emerged as the first therapeutic option due to high success and low complication rate. (1, 2) Pediatric EP is closely related to the adult EP, but there are some very important differences in preparation and approach as well as characteristics of arrhythmogenic substrates. Children undergoing invasive EP represent a unique population different from adult patients undergoing similar procedure. The pediatric EP programme in University Hospital Centre “Sestre milosrdnice” started officially in March 2018. in collaboration of Pediatrics and Cardiology Clinics. In last 7 months, 23 (14 male, 9 female) pediatric patients underwent EP procedure. After EP study 20 patients successfully underwent radiofrequency catheter ablation and one patient underwent cryoablation. Two patients underwent EP study only – one with benign accessory pathway and one with PVCs that originate from left coronary cusp near the ostium of left coronary artery. 18 patients were diagnosed with supraventricular tachycardia (13 accessory pathways and 5 with atrioventricular nodal reentry tachycardia). 2 patients were diagnosed with PVCs (one from RVOT and one para hisian). All 23 EP studies were performed with 3D mapping system (Ensite Precision) and catheters suitable for children (5F catheters when needed). Youngest child with left lateral accessory pathway and AVRT was three years old. 17 procedures were performed completely without the use of fluoroscopy, while in 6 cases minimal fluoroscopy time was used for the transseptal puncture and in one case coronary angiography had to be performed. No complications occurred. Precisely because of the complexity, standardization of the procedures and the use of custom protocols increases the quality of care and pediatric patient safety and improve ablation outcome.