bjectiveTo compare the values of endobronchial ultrasound guided transbronchial needle aspiration (EBUS-TBNA) and positron-emission tomography and computed tomography (PET/CT) in diagnosis of enlarged mediastinal lymph nodes caused by unknown reasons, and to study the diagnostic value of the combination of EBUS-TBNA and PET/CT. MethodsA retrospective study was carried out in our hospital. From December 2010 to August 2011, a total of 45 patients with enlarged mediastinal lymph nodes received EBUS-TBNA following PET/CT examination. Conventional bronchoscopy was performed before EBUS-TBNA. The patients with endobronchial lesions were excluded from this study. Patients with negative EBUS-TBNA results underwent surgical biopsies or a minimum of 6 months’ clinical and radiological follow-up. ResultsSensitivities of EBUS-TBNA and PET/CT in diagnosis of enlarged mediastinal lymph nodes were 81.48% (22/27) and 92.59% (25/27), the specificities were 100% (18/18) and 55.56% (10/18), the positive predictive values (PPV) were 100% (22/22) and 75.76% (25/33), the negative predictive values (NPV) were 78.26% (18/23) and 83.33% (10/12), the accuracies were 88.89% (40/45) and 77.78% (34/45), respectively. EBUS-TBNA had a significantly better specificity (P=0.003) and PPV (P=0.016) than PET/CT for diagnosis of enlarge mediastinal lymph nodes. ConclusionEBUS-TBNA is valuable for diagnosing enlarged mediastinal lymph nodes caused by unknown reasons. EBUS-TBNA combined with PET/CT can reduce the false negative results in diagnosis of malignant mediastinal lymph nodes.