CT is very useful to find small amount of free air in abdominal cavity. To determine the most appropriate treatment, it’s very important to detect the perforating site, which has been pointed out by emergent endoscopy and/or upper GI radiological examination so far. However, these examinations are so invasive for this kind of patients. AIM: to clarify characteristics of PGU and PDU, and possibility whether CT can differ PGU from PDU. METHOD: medical records and CT of 37 patients(Pts) who were treated in our hospital in recent three years, were retrospectively reviewed. RESULT: mean age of the Pts are 61 in PGU (14Pts), and 48 in PDU (23Pts). 26 Pts (70%) did not have past history of peptic ulcer. Abdominal pain suddenly occurred in 17Pts (46%), though 20Pts (54%) noticed worsening symptom of peptic ulcer at least 24 hours before admission. Only 3 cases were under the medical treatment of peptic ulcer at the time of admission. HP positive rate were 25% in PGU and 91% in PDU. Non-surgical, conservative therapy was adopted according to following criteria, 1. Less than 65 years old, 2. Hospital arrival in less than 6hours after severe symptoms occurred, 3. Do not have serious general complications, 4. Accumulating small amount of ascites localized in the subphrenic cavity. Conservative therapy consists of 1. fasting 2. proton pump inhibitor i.v. 3. antibiotics i.v. 4. insertion of nasogastric tube and drained by 10cmH2O. PDU were cured by conservative therapy in 15Pts(65%), while PGU were in only one Pts(0.7%). Surgical management include omental plombage+drainage (12Pts), drainage only (4Pts), gastrectomy (1Pts), and selective proximal vagotomy+pyloplasty (2Pts). 2Pts (PDU) were converted from conservative to surgical management. Duration of nasogastric tube, fasting, and hospital stay were 4.7, 7.8, 15.1 days respectively in non-surgical group vs 9.3, 12.2, 28.3 days in surgical group. In all cases, perforating sites were diagnosed with initial CT reviewed by radiologist, which had been confirmed by operation and/or endoscopy. Conclusion: PGU usually need surgical management, while PDU do not. We can differ PDU from PGU by CT reviewing without endoscopy. Careful reviewing CT will promise us with early and non-invasive decision making of treatment method and good clinical outcome in patients with PGU and PDU.