©2020 NRITLD, National Research Institute of Tuberculosis and Lung Disease, Iran.Background: Postoperative pulmonary complications (PPC) are important problems that prolong hospital stays by increasing morbidity and mortality of patients. Early identification of risky cases through preoperative evaluation is important for reducing the complications that may be seen in patients postoperatively. The aim of this study is to calculate, evaluate and compare the risk indices for PPC in patients who will undergo elective abdominal surgery. Materials and Methods: One hundred twenty-four patients who were hospitalized for elective abdominal surgery were included in this prospective observational study. American Society of Anesthesiologists (ASA), Epstein and Shapiro scores, respiratory failure index (RFI), pneumonia risk indexes (PI) and scores were calculated preoperatively. Patients were re-evaluated at the 48th postoperative hour, and one-week follow-up was performed. The patients with PPCs are recorded. Results: The mean PPC rate was 36.8%. Based on this, pleural effusion was observed in 18.5%, prolonged mechanical ventilation in 8.9%, atelectasis in 9.7%, and respiratory failure in 5.7%, bronchospasm in 4.0%, and pneumonia in 3.2% of patients. An increased risk in PPC was determined if ASA were above 3 (odds ratio, [OR], 7.06; <0.001), PI scores were above 3 (OR, 6.67; <0.001), RFI score were above 4 (OR, 6.30, p:0.001) and Shapiro score above 2 (OR, 20.01; <0.001), respectively. Conclusion: The Shapiro index is the strongest predictor of pulmonary complications, whereas the PI is the strongest predictor of morbidity risk. However, RFI and the PI are equally valuable for predicting respiratory complications and may prove to be useful in abdominal surgeries for preoperative assessment.