Associations between diverticular disease of the colon and the colorectal cancer has been studied for >60 years. Observational, cross-sectional, and case-control studies as well as large population-based studies gave conflicting results and association was not fully proven. Obtaining the proof was difficult because both diseases share similar clinical characteristics, both increase with age, and both involve similar dietary factors. Long-term observations are difficult as diagnostic methods changed over time from barium enema 50 to 60 years ago, through endoscopy, up to CT and MR in recent years. Cancer or adenomas may be missed within diverticular segment; diverticula may be underreported in patients with colon cancer diagnosis. Most recent 2 large cohort studies have solved the dilemma. These studies have clearly shown that diverticular disease does not increase the risk of colon cancer after the first year of diagnosis. Within the first year of diagnosis the association is strong, most probably due to difficulties with differential diagnosis and misclassifications and shared symptoms. Findings of these studies have led to the conclusion that colon cancer has to be excluded using modern techniques after the first episode of suspected diverticulitis.