Background: A post-operative pulmonary complications (PPCs) is a major cause of prolonged hospital stay, mortality. PPCs-related risk factors investigated in previous studies do not reflect current change, and risk stratification to estimate PPCs still remain unclear. Methods: We retrospectively analyzed the clinical data of 2,059 patients who received preoperative evaluation from respiratory physicians between June 2011 and October 2012. Continuous variables were changed to dichotomous variables with best cut-off points to estimate PPCs using receiver operating characteristic curve. Multiple logistic regression models were conducted to develop prediction model for estimating PPC. New scoring system for estimating PPCs was developed by using beta coefficients of final multiple regression models. Results: Of 2,059 patients studied, 140 patients (6.8%) had PPCs; 33 in respiratory infection, 71 in respiratory failure, 38 in pleural effusion, 35 in atelectasis, 5 in bronchospasm, and 1 in pneumothorax. Multiple logistic regression model revealed six independent risk factors with scoring in parenthesis: age ≥70 yr (2 points), current smoker (1 point), the presence of COPD (1 point), ASA class ≥2 (1 point), serum albumin ＜4 g/dl (1 point), and thoracic and abdominal surgery without laparoscopic technique (4 points). The area under the curve was 0.79 (95% CI, 0.75-0.83) with new development model. Conclusion: The new risk stratification with 6 variables has excellent discriminative ability to estimate PPCs. Further research is needed to validate this new prediction rule.Background: A post-operative pulmonary complications (PPCs) is a major cause of prolonged hospital stay, mortality. PPCs-related risk factors investigated in previous studies do not reflect current change, and risk stratification to estimate PPCs still remain unclear. Methods: We retrospectively analyzed the clinical data of 2,059 patients who received preoperative evaluation from respiratory physicians between June 2011 and October 2012. Continuous variables were changed to dichotomous variables with best cut-off points to estimate PPCs using receiver operating characteristic curve. Multiple logistic regression models were conducted to develop prediction model for estimating PPC. New scoring system for estimating PPCs was developed by using beta coefficients of final multiple regression models. Results: Of 2,059 patients studied, 140 patients (6.8%) had PPCs; 33 in respiratory infection, 71 in respiratory failure, 38 in pleural effusion, 35 in atelectasis, 5 in bronchospasm, and 1 in pneumothorax. Multiple logistic regression model revealed six independent risk factors with scoring in parenthesis: age ≥70 yr (2 points), current smoker (1 point), the presence of COPD (1 point), ASA class ≥2 (1 point), serum albumin ＜4 g/dl (1 point), and thoracic and abdominal surgery without laparoscopic technique (4 points). The area under the curve was 0.79 (95% CI, 0.75-0.83) with new development model. Conclusion: The new risk stratification with 6 variables has excellent discriminative ability to estimate PPCs. Further research is needed to validate this new prediction rule.