Many common bite problems are caused by underlying jaw size discrepancies. For example, a patient that presents with protruding upper incisors will often have an underdeveloped lower jaw. In other cases, an “underbite” may be caused by underdevelopment of the upper jaw or an excessively long lower jaw.These structural jaw anomalies and associated bite problems can be addressed in young growing patients by manipulating the jaw growth with functional orthopaedic appliances. Such treatment is timing critical and must be considered in the context of the patient’s dental, physical and psychological development together with their long-term treatment plan. An orthodontist is the most qualified practitioner to advise on the suitability of this form of treatment.