Preoperative pulmonary assessment is an essential step in the selection and the management of patients who are candidates for thoracic procedures. Despite advances in anesthesia, including the use of epidural analgesics, and advances in surgical techniques and perioperative care, postoperative pulmonary complications remain the leading cause of morbidity and mortality in thoracic surgery. No single parameter is predictive of postoperative complications or mortality in patients who undergo a thoracic procedure. Therefore, patients should not be denied for surgical resection based on any single abnormal test or parameter. A comprehensive assessment of the functional status, exercise tolerance, and pulmonary function should be performed before surgery to select the patients appropriately, predict the risk of postoperative complications, and achieve better outcomes.