Lung cancer is one of the most common malignant tumors in the world and with the highest incidence in China. Surgery is the most effective therapeutic method for primary lung cancer. Accurate prediction of residual postoperative pulmonary function in patients, especially those with borderline pulmonary function, is crucial for proper qualification for surgery. According to the 3rd American College of Chest Physicians(ACCP) evidence-based clinical practice guideline (2013), both predictive postoperative (ppo) FEV1.0% and ppoDLCO% are greater than 60% predicted are required as a first standard of lobectomy for patients with primary lung cancer. And, according to the British Thoracic Society (BTS) guideline, patients with ppoFEV1.0% and ppoDLco% less than 40% have high a risk for surgery. Pulmonary ventilation / perfusion SPECT/CT has recently become available for prediction of lung function, and it can be used to forecast pulmonary function in consideration of the pulmonary circulation as well as effective residual lung function. Traditionally, prediction of postoperative lung function was based on planar method in anterior and posterior projections of lung scintigraphy. However, SPECT/CT enables measurement of ventilation / perfusion uptake in each lobe of the lungs in a three dimensional way, which may avoid underestimating ppoFEV1.0% and provide confidence in suggesting lobectomy or pneumonectomy. This experiment is intended to explore the use of Q.lung, a volume-based software to semi-quantitatively calculate pulmonary ventilation/perfusion functional uptake and volume by SPECT/CT. We hope it can get a more accurate prediction of postoperative residual pulmonary function to provide better management for clinical surgery.