Ventricular preexcitation syndromes (VPS) are very important between cardiac rhythm disturbances in childhood, because their presence can change the clinical and ECG picture and thus the treatment can be very difficult. The authors studied 58 cases of VPS in children (2 weeks-15 years old) admitted in a period of 3 years. The surface ECG showed VPS aspects: in 30% of cases we noticed WPW syndrome type B and the rest presented VPS with Mahaim pathways and Lown-Ganong-Levine syndrome. 4 cases were familial and 1 child a hidden WPW syndrome. In 65% of cases the cardiac symptoms put the diagnosis and 1/3 of cases were discovered by common ECG. The most important cardiac sign of the children with WPW syndrome was the paroxysmal supraventricular tachycardia, 4 cases presenting wide QRS complex. Others types of VPS were without clinical symptoms. The intravenous administration of digoxin + propranolol was the therapy of choice for paroxysmal supraventricular tachycardia in infants and children until 2-3 years old, and propranolol and chinidine after this age. The children older than 2-3 years and/or those with ineffective preventive for recurrent treatment received dysopiramide and specially amiodarone with satisfactory results; it was not necessary the surgical ablation of the aberrant pathway. Ventricular preexcitation syndromes and wrong treatment can induce severe ventricular arrhythmia, so all the tachyarrhythmias with unknown etiology and especially those with wide QRS complex must be investigated very carefully, using and Holter test and the endocavitary electrophysiology, for a correct medical and/or surgical treatment.