The basic therapeutic principles in paediatric chest physiotherapy (CPT) are identical to those applied in adults. However, the child's growth and development results in continuing changes in respiratory structure and function, and the requirement for different applications of CPT in each age group. Forced expiratory manoeuvres and coughing serve as basic mechanisms for mobilization and transport of secretions, but the reduced bronchial stability after birth requires special techniques in very young patients. High externally applied transthoracic pressures have to be avoided in order to prevent interruption of airflow. In addition, airway patency is maintained by the application of back pressure and by liberal use of continuous positive airway pressure. Since sympathomimetic bronchodilators might further decrease bronchial stability, their use must be individualized in newborns and young infants. Inspiration is a basic mechanism for inflating alveolar space behind obstructing mucus plugs. Due to a highly unstable chest, the premature baby, newborn and infant cannot distend their lung parenchyma to the same extent as can older patients. Consequently all chest physiotherapy strategies applied in this age group have to incorporate appropriate techniques for raising lung volume. Positioning serves to redistribute ventilation, but the young infant's response to gravitational forces differs substantially from that of the adult, and consequently strategies used in older patients have to be modified. In addition, the therapist has to consider pathology such as bronchial instability lesions and airway hyperresponsiveness and has to adjust the therapeutic response accordingly. It is particularly important to consider the special vulnerability of newborns and young infants and to modify therapeutic interventions to avoid the harm that could otherwise be inflicted. Consideration of these differences between infant, child and adult and careful analysis of the available mucus clearance techniques allows tailoring of an individualized therapeutic approach to the paediatric patient.