In providing orthodontic care for paediatric patients, clinicians often questions whether to begin treatment early-during the primary or early-transitional dentition-or wait until all or most of the permanent teeth are present. A comprehensive knowledge is necessary for planning the implementation of preventive therapy or the choice for interception is left. Early orthodontic treatment is effective and desirable in specific situations. The early treatment eliminates noxious habits, re-orientates dental-maxillary development and compensates for the structural discrepancy between teeth and bone. This leads to a timely correction of defects, which could have a negative aesthetic impact, therefore, contributing effectively to a better harmonization of the child with the human environment where he lives, and improving his feelings of acceptance within it. However, the evidence is equally compelling that such an approach is not indicated in many cases for which later, single-phase treatment is more effective. Therefore, clinicians must decide, on a case-by-case basis, when to provide orthodontic treatment.