Background Integrated positron emission tomography and computed tomography (PET/CT) is increasingly used for the preoperative nodal staging of non-smail cell lung cancer (NSCLC).The aim of this study was to evaluate the accuracy of PET/CT in comparison with CT in detection of nodal metastasis and preoperative nodal staging in patients with NSCLC,and to analyze the causes of the PET/CT false-negative and false-positive results.Methods Consecutive patients with pathologically proven NSCLC who underwent staging using PET/CT from July 2008 to February 2012 were evaluated retrospectively.Nodal staging was pathologically confirmed on tissue specimens obtained at thoracotomy.The accuracy of PET/CT and CT in the assessment of intrathoracic nodal involvement was determined using histological results as the reference standard.Logistic regression was used to define the causes of the false-negative and false-positive results.Results A total of 528 lymph node stations were evaluated in 101 patients.Lymph nodes were positive for malignancy in 43 out of 101 patients (42.6％),and 101 out of 528 nodal stations (19.2％).PET/CT was significantly more accurate for nodal staging than CT.The sensitivity,specificity,positive and negative predictive values,and accuracy of PET/CT for detecting nodal metastasis were 51.5％,95.8％,74.3％,89.3％,and 87.3％ and the corresponding data by CT were 45.5％,87.1％,45.5％,87.1％,and 79.2％,respectively.PET/CT confers significantly higher specificity,positive predictive value,and accuracy than CT in detecting nodal metastasis.False-negative results by PET/CT are significantly associated with smaller lymph node size,whereas false-positive results are related to a combination of inflammatory disorders and larger lymph node size.Conclusion PET/CT confers significantly higher accuracy than CT in nodal staging,and is more specific and accurate than CT in detecting nodal metastasis but has a low sensitivity and high false-negative rate.