Arrhythmias are the main cause of morbidity and mortality in adult patients with congenital heart disease. Arrhythmias can be due to the primary anatomical defect or they can be a consequence of the long term effects of haemodynamical defects and surgical repairs. Atrial arrhythmias are the most frequent form and their prevalence varies between 10-60% in different congenital defects. Ventricular tachycardia are less common but they have potentially a dramatic impact on survival. When correcting the haemodynamic defect is not effective in avoiding arrhythmias complications, it is necessary to apply specific therapy. Antiarrhythmic drugs must be used very carefully, there is an increasing application for transcatheter or surgical ablation and device implantation.