PURPOSE: To compare the diagnostic efficacies of integrated (18)F FDG PET/CT images and contrast-enhanced helical CT images in locoregional lymph node metastasis in the patients with non-small cell lung cancer (NSCLC). METHODS: From June 2005 to June 2007, 122 potentially operable patients with proven or suspected non-small cell lung cancer underwent integrated PET/CT and contrast-enhanced CT scans followed by surgical nodal staging. The results of reviewing PET/CT and enhanced CT images for the locoregional lymph node metastasis were compared in relation to pathologic findings. RESULTS: Preoperative nodal staging was compared with postoperative histopathological staging, 80% (98 of 122) of patients correctly staged, 13% (16 of 122) of patients were overstaged, and 7% (8 of 122) were understaged by PET/CT, while those values for CT were 56% (68 of 122), 26% (32 of 122), and 18% (22 of 122), respectively. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of PET/CT for lymph nodes were 86%, 85%, 85%, 64%, 95%, respectively; compared with 69%, 71%, 70%, 43%, 88% for CT (P=0.000, 0.000, 0.000, 0.001, 0.001, respectively). 81% false-negative interpretations and 72% false-positive interpretations on CT were corrected by PET/CT. 57% false-negative interpretations and 45% false-positive interpretations on PET/CT were corrected by CT. 6 % (9 of 153) positive lymph nodes and 8% (40 of 486) negative nodes at pathology were incorrectly diagnosed both by PET/CT and CT. CONCLUSION: Integrated PET/CT improves the sensitivity, specificity, accuracy, positive predictive value, and negative predictive value than enhanced CT in the assessment of locoregional lymph nodes, and provides more efficient and accurate data of nodal staging, with a better effect on diagnosis and therapy in non-small cell lung cancer.