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This study was designed to make a retrospective analysis of imaging factors which improve the positive predictive values (PPVs) in NSCLC and to discuss the role of CT in mediastinal (N2) disease staging. Between 1982 and 1997, 90 patients with enlarged mediastinal lymph nodes (MLNs) on CT underwent surgical staging. The overall PPV was 44% and the PPVs on a station-by-station basis were 28 to 40%. A logistic regression model showed that tumors larger than 3 cm (p=0.01) and enlarged hilar lymph nodes (p<0.01) were significant predictors of N2-disease. When the two factors were combined, the overall PPV and the PPVs on a station-by-station basis improved to 74% and 54 to 60%, respectively. These results are not sufficiently reliable for clinical use and histologic confirmation is mandatory. CT defines mediastinal anatomy and can help the surgeon in the selection of the most appropriate procedures to evaluate N2-disease. CT and invasive procedures are complementary in the staging of NSCLC.