Postoperative pulmonary complications frequently lead to increased patient morbidity and mortality, hospital length of stay, and resource utilization. Atelectasis and infectious complications account for the majority of reported pulmonary complications. Risk factors are thought to exaggerate pulmonary function deterioration, which occurs both during and after surgical procedures. This article reviews the literature and describes risk factors frequently identified in relation to pre-, intra-, and postoperative settings, impact of each risk factor on pulmonary function, and issues related to risk factor evaluation. Eighteen risk factors are reviewed regarding their pathophysiologic impact on pre-, intra-, and postoperative pulmonary function. Key issues related to risk factor evaluation are also discussed. Identification of risk factors and prediction of postoperative pulmonary complications are important. Early identification of patients at risk for postoperative pulmonary complications can guide our respiratory care to prevent or minimize these complications.