Purpose : To clarify clinical features of appendiceal diverticulitis comparing with acute appendicitis. Methods : Among a series of 428 patients who underwent appendectomy for preoperative diagnosis of acute appendicitis or appendiceal diverticulitis and had comprehensive preoperative blood data, 344 patients histopathologically diagnosed with appendiceal diverticulitis (n=20) or acute appendicitis (n=324) were enrolled in the study. Clinical factors, including age, sex, body height, body weight, body mass index (BMI), association of abscess or perforation, and blood data taken immediately before surgery, were comparatively investigated between the two groups. Results : White blood cell count, neutrophil/lymphocyte ratio, alanine aminotransferase (ALT) in the appendiceal diverticulitis group were significantly lower than those in the acute appendicitis group (p<0.05), although there was no significant difference in age, sex, and BMI between the two groups. Total protein in the former group was higher than that in the latter group (p<0.05). Multivariate analysis showed that lower preoperative serum albumin, elevated ALT, and pathological appendiceal diverticulitis were significant independent factors for association of abscess or perforation. Prevalence of abscess or perforation in the appendiceal diverticulitis group was significantly higher than that in acute appendicitis group (30% vs 12%, relative risk : 2.5, odds ratio : 4.22, 95% confidence interval : 1.27-13.11, p=0.021). Conclusions : Appendiceal diverticulitis was more often associated with abscess or perforation despite with lower inflammatory reaction than acute appendicitis.