Abstract: The inventive masks and medical gas-delivery systems make possible delivery of medical gases (such as oxygen) to pediatric patients with faces too small to be comfortably served by conventional masks and systems sized for adults. The inventive masks minimize the surface area of the baby's face being covered and also balance tubing and related parts contacting the baby. In addition, it allows efficient delivery of required pressure, while minimizing any leak of delivered oxygen or gas outside the breathing system.