The paper gives the view of the author who is based on his many-year experience in studying a role of radiation diagnosis of colon cancer. It shows it necessary to enhance the significance of radiation diagnosis. More attention should be given to the traditional section on the current radiation study of the large bowel: to irrigoscopy and single double contrasting. By taking into account the labor-consumption of irrigoscopy, the author suggests that the procedure should be simplified without losing its diagnostic capacities. However, he considers single double contrasting of the bowel to be the optimum technique of traditional X-ray study of the bowel in detecting its tumors. Pneumocolonoscopy and iliocecal node study of the ileocecal angle are given in the paper as supplementary techniques of traditional X-ray study of the large bowel. Emphasis is also placed on the role of radiation diagnostic techniques, such as ultrasound diagnosis, X-ray computed tomography, and magnetic resonance imaging. By highly appreciating their significance in the diagnosis of colon cancer, the author believes that they should play a role of important, but additional ways of detecting this pathology. By pointing out the excellent capacities of fibrocolonoscopy, as applied to the problem discussed in the paper, the author does emphasize the certain limitations of this technique, by taking into account that its application can cause some complications. The author's opinion that the obvious increase in the incidence of endophytic carcinomas drastically enhances the role of their radiation diagnosis, but by obligatorily correcting currently available principal methodic and semiotic directives, runs through the entire paper.