The ECG in children has a number of characteristic differences compared to the ECG of the adult. The transition of the ECG in neonates after birth represents dynamic changes of the circulatory system due to the postnatal adaptation, different physiologic properties of the fetal and neonatal myocardium, the location and orientation of the heart in the chest and influence of body mass during that period and later on in childhood. The ECG is an obligatory diagnostic tool in childhood arrhythmias. The complexity of changes implies a broad variation of ECG changes during the first days and weeks of life, whose interpretation requires expert knowledge. Audience Take Away: • The neonatal changes of the ECG are extreme. The knowledge of these changes explains the presentation of ECG during childhood. • Preventing misinterpretation of the ECG in Childhood. Explains why routine ECG/screening in the very young is not very useful.