Three patients with large fatty retroperitoneal tumours are presented. In all three the fatty mass was visible (but initially not recognized as such) on plain abdominal radiographs. Computed tomography (CT) confirmed the presence of fat within these tumours. Attention is drawn to the importance of the correct interpretation of the plain abdominal radiograph when such fatty tumours are present. Computed tomography then proves the presence of fat as well as site of origin of such tumours.