Abstract: Objective To evaluate the clinical value of presurgical CT in diagnosis of TNM staging in NSCLC through comparing with corresponding postoperative pathology. Methods A total of 112 patients with NSCLC as clinical phase Ⅰ～ⅢA  proved by pathological features received spiral CT. After the mediastinal lymph node dissection and tumor resection,the spiral CT findings and corresponding pathologic results in TNM staging were compared. The sensitivity,specificity and accuracy of presurgical CT scan for diagnosis of TNM staging were evaluated. Results Compared with corresponding pathologic results in T category,the overall sensitivity and specificity were 76.6% and 85.7% respectively;the positive predictive value was 92.2%,and the negative predictive value was 62.5%.The accuracy was 79.5%（Kappa=0.658，P<0.05）；(2) as for mediastinal lymph node category,the overall sensitivity and specificity were 72.9%,84.9% respectively.The positive predictive value was 84.3% and negative predictive value was 73.8%.The accuracy was 78.6%（Kappa=0.667，P<0.05）.The accuracy and specificity of spiral CT were relatively low in staging 4R,5,6 lymph node groups;and the false negative and false positive rates were high in staging 4R lymph node groups. Conclusion The clinical TNM staging based on preoperative CT scan is valuable but not very accurate.The high false negative and positive predictive value of CT in T and N category may hamper its clinical application.Other methods such as PET-CT and mediastinoscopy should be combined for elevating the accuracy of TNM staging.