Morbid obesity and its association with obstructive sleep apnoea syndrome have been increasingly recognised in children. Orthopaedic surgeons are often the primary medical contact for older children with tibia vara, which has long been associated with obesity, but are unfamiliar with the evaluation and treatment of sleep apnoea in children. We reviewed all children with tibia vara treated surgically at one of our institutions over a period of five years. Thirty-seven patients were identified; 18 were nine years of age or older and 13 of these (72%) had morbid obesity and a history of snoring. Eleven children were diagnosed as having sleep apnoea on polysomnography. The incidence of this syndrome in the 18 children aged nine years or older with tibia vara, was 61%. All these patients required pre-operative non-invasive positive-pressure ventilation; tonsillectomy and adenoidectomy were necessary in five (45%). No peri-operative complications related to the airway occurred. There is a high incidence of sleep apnoea in morbidly obese patients with tibia vara. These patients should be screened for snoring and, if present, should be further evaluated for sleep apnoea before corrective surgery is undertaken.