Appendicitis can be a difficult clinical diagnosis to make. A negative appendicectomy rate of 20% has traditionally been accepted as the consequences of appendiceal perforation can be grave. Cross-sectional imaging is increasingly being employed in the investigation of adults with suspected appendicitis. This review will demonstrate the appearance of the normal appendix on computed tomography (CT) and its appearance in a range of inflammatory and neoplastic processes including appendicitis, Crohn's disease, infections, and benign and malignant tumours.