Congenital diaphragmatic hernia (CDH) has an incidence of 1 in 2500 live births in the UK. CDH is a defect in the fetal diaphragm which allows the contents of the abdominal cavity to protrude into the thorax. CDH may be associated with other major anomalies. The defect may be diagnosed in the fetus, newborn or older child. Some forms of CDH may remain ‘asymptomatic’ for several years and not present until later life or adulthood. CDH is most often a sporadic and isolated birth defect (70%) though a number of gene mutations have been identified, e.g. chromosome 4p, 8q, 15q. Links have been made to environmental factors such as thalidomide, nitrofen and vitamin A deficiency. CDH may also be associated with the chromosomal disorders trisomy(s) 13, 18 and 21 including the inherited conditions—Fryn’s and Pallister Killian syndromes.