Duplication cyst is an uncommon congenital abnormality of the alimentary tract. It can occur anywhere in the alimentary tract with the ileum and the jejunum representing the most common sites of duplication. Most often the patients are asymptomatic and colonic duplication cysts remain undiagnosed for years. In this case report we present an unusual case of colonic duplication cyst with a transverse colon location. We present the radiological findings of this rare congenital malformation in order to be included in the differential diagnosis of cystic masses of the gastrointestinal tract.