Background: Catheter ablation (CA) therapy is the first-choice treatment in adults with heart rhythm disturbances. Arrhythmias in adults are mainly conditioned by coronary artery disease. Aetiology of arrhythmias in children is mostly associated with inherited heart disorders. According to the current guidelines, CA is widely used in children, indicating the need to make it more achievable in the paediatric population. Aim: To assess the efficacy and safety of CA in children with different types of arrhythmias on the initial learning curve at a newly built Ablation Centre in the Independent Paediatric Hospital of the Medical University of Warsaw, Poland. Methods: The study population comprised 32 children with supraventricular tachycardias, asymptomatic pre-excitation syndrome, or ventricular ectopic beats undergoing CA. The mean age of the study population was 14.1 ± 2.4 years. In all patients, electrophysiological study (EPS) and CA were performed. Analysis with respect to procedure duration, fluoroscopy exposure duration, location of accessory pathways (AP), success rate, recurrences, and complications was performed. Results: The mean procedure duration was 105.4 ± 41.4 min (range 40–175 min). The mean fluoroscopy duration was 8:34 ± 5:01 min (range 1:28–21:01). The mean exposure to ionising radiation was 4.7 ± 3.2 mcG/kg. EPS revealed signifi¬cantly more frequent presence of AP in the left side (57.1%). The radiofrequency ablation procedure was successful in 26 of 32 (81.3%) children, and cryoablation was successful in two of four patients. In two (6.3%) children minor complications occurred. Conclusions: Catheter ablation may be effectively performed without major complications in the initial phase of the learning curve if a reasonable approach with a gradual increase of the procedural complexity is taken.