Heliox is composed of oxygen and helium and its low specific gravity allows a modification of the gas flow within the airway. Breathing heliox favors a laminar flow and therefore decreases the work of breathing. Its usefulness in the child is established in croup or in post-extubation stridor. It can be considered if conventional treatment fails to improve the child's breathing pattern. Its major goal is to avoid invasive manoeuvers as much as possible.