Diverticulosis may have a diverse set of complications and comorbidity, one of which is a giant diverticulum. This single air-filled bubble, with a diameter of 4 cm or more, can evolve from a pseudodiverticulum by two pathways: by secondary infection or by means of a so-called ball-valve mechanism. Perforation of an infected pseudodiverticulum into a colonic duplication cyst can result in the same clinical and radiological findings. In our case report, we present a patient with a duplication cyst of the colon, which is rarely found at other locations than the small bowel.