Background: Radiofrequency ablation (RFA) of the atrioventricular accessory pathway (AP) has been proven to be a very safe and effective therapeutic modality in symptomatic and asymptomatic Wolff-Parkinson-White (WPW) patients providing an essential ���cure��� for more than 95%. In previous studies, the effective refractory period of the AP and its conduction changed with age, and this is particularly well known in young children. The aim of this study was to evaluate the clinical and electrophysiological characteristics of the subjects with WPW syndrome below 30 years of age. Methods: Two-hundred and twenty-one consecutive patients with WPW syndrome, who has undergone electrophysiologic study (EPS), aged 6-75years, were recruited; 73(33%) of these patients were <30 years of age. EPS was indicated for suspected or documented tachycardias, syncope or was systematic in asymptomatic patients. The location of the accessory pathway was confirmed by EPS. The clinical, electrophysiological and therapeutic data for these patients were evaluated by retrospective medical record review. Results: Sixteen boys and 15 girls (group 1), aged 6-17 years, and 31 men and 11 women (group 2), aged 18-29 years were admitted for EPS and ablation. In comparison with group 1, male were more than female in group 2 (P=0.029). Among group 1, 2 patients had congenital heart disease (Ebstein anomaly) and 1 patient had dilated cardiomyopathy. Four patients had syncope (1 of group 1, 3 of group 2) and 12 patients were asymptomatic (8 of group 1, 4 of group 2, P=0.064). Left side accessory pathway was detected more frequently in group 2 (57%) than in group 1 (26%) (P=0.035); multiple accessory pathway was detected in 6 patients (4 of group 1, 2 of group 2, P=0.211). Anteroseptal location which was associated with a risk of complete AV block did not differ significantly in group 1 (3/31) and in group 2 (2/42) (P=0.411). Atrial fibrillation was more frequent in group 2 (12% vs. 3%), but it was not significant difference (P=0.182). RFA of the AP was indicated 79 times, and 6 of the patients recurred (3 of group 1, 3 of group 2); the incidence of ablation failure was more frequent in group 1 (11%) than in group 2 (2%) although it was not significant difference (P=0.079). Conclusion: In children and adolescence with WPW syndrome, the detection of right side AP was more frequent. The incidence of asymptomatic and abnormal electrocardiogram, atrial fibrillation and ablation failure also was more frequent although those did not differ significantly as compared with adult. In conclusion, when EPS and RFA are done in the young population with WPW syndrome, we recommend that these characteristics should be considered.