PURPOSE: Management strategy in acute appendicitis patients initially presenting with abscess or mass is surrounded with controversy. This study was performed to identify the outcomes of management for this condition. METHODS: We retrospectively analyzed prospectively registered 76 patients (male:female = 39:37; mean age, 50.8 years) with appendicitis presenting with abscess or mass over a 9-year period at the Seoul National University Hospital. Patients were divided into three groups (emergency operation group, delayed operation group, and follow-up group), and clinical characteristics and outcomes of treatment were investigated. RESULTS: Twenty-eight patients (36.8%) underwent an emergency operation. Of the remaining 48 patients, 20 (41.7%) were initially treated with conservative management through the use of antibiotics only; the other 28 (58.3%) with and additional ultrasound-guided percutaneous drainage of the abscess. Twenty-six (54.2%) patients underwent planned operations after conservative management, and 22 (45.8%) were followed without surgery (median duration, 37.8 month), of which 3 (13%) underwent an appendectomy due to recurrent appendicitis (mean of 56.7 days after initial attack). There were no statistical differences in types of operation performed (appendectomy or ileocecectomy), postoperative complications, and postoperative hospital stay among the patients who underwent emergency operations, delayed operations and operations for recurrence during follow-up. CONCLUSION: Although the recurrence rate was relatively low after conservative management for appendicitis patients presenting with abscess or mass, there was no difference in surgical outcome between the emergent, elective, or recurrent groups. Our results indicate that proper management of appendicitis with abscess or mass can be selected according to surgeon's preference.