Duplication cysts of the gastrointestinal tract are rare congenital abnormalities. Ectopic gastric mucosa, which can be found in duplications, may cause peptic ulceration, gastrointestinal bleeding or perforation. We report a 1-year-old boy with a perforated ileal duplication cyst with haemorrhagic pseudocyst formation caused by peptic ulceration of the duplication cyst. It presented a snowman-like appearance consisting of a small, thick-walled, true enteric cyst and a large, thin-walled haemorrhagic pseudocyst on US and CT. It is an unusual manifestation of a duplication cyst, which has not been reported in the English language literature.