PURPOSE: With the gradual changes in the diet, the incidence of colonic diverticular disease, particularly that of the left side colon, has increased rapidly in Korea. The aim of this study was to evaluate the clinical features of diverticular disease and to compare the differences in treatment between right and left colonic diverticulitis. METHODS: The hospital records of 67 patients with diverticulitis were reviewed retrospectively. RESULTS: The incidence of right side colonic diverticulitis was 2.5 times higher than that of the left side (48 and 19 cases, respectively). The mean age of the patients was 51.3 years with a male to female ratio of 2.1:1. The left side colonic diverticulitis developed at an older age than that of the right side (mean age of 47.2 and 58.7 years, respectively, P= 0.03). Seventeen out of 48 (35.4%) right and 8 out of 19 (42.1%) left colonic diverticulitis patients were treated surgically. The ratio of surgical treatment was not different according to the location of diverticulitis (P=0.61). The age and gender of the patients or leucocytosis at the time of the diagnosis were not associated with the risk of surgical treatment. The presence of fever and high-grade sepsis on the CT scan (Hinchey grade) were significant risk factors for surgery. The symptom duration was longer in the surgically treated group than in the conservative treatment group in left colonic diverticulitis (P=0.03). Most surgical procedures for right colonic diverticulitis were a single-stage colon resection (16 out of 17 cases), whereas staged procedures including Hartmann's operation (3 cases) and proximal diversion (2 cases) with abscess drainage were performed in 5 out of the 8 left colonic cases. Postoperative complications were more frequent in the left colon cases. CONCLUSION: The left colon is a relatively rare site for diverticulitis in Korea. However, diverticulitis of this section of the colon requires more complicated surgical treatment and is associated with a higher rate of complications than that of the right colon. The earlier application of diagnostic work up might be necessary for patients suspected of having left colonic diverticulitis because a delayed diagnosis is associated with a risk of surgical treatment.