Computed tomography (CT) has become the imaging modality of choice for the investigation of patients with clinico-radiological suspicion of obstruction. Appropriate CT technique is discussed, with recommendations on how to improve diagnostic confidence and to reduce radiation dose. The performance of CT in the investigation of LBO is compared to that of the plain abdominal radiograph and contrast enema. CT is unrivalled in its ability to detect and characterise the cause of large bowel obstruction (LBO), identify complications, and guide appropriate treatment.