The purpose of the study was to investigate whether glucose transporter type 1 (Glut-1) mediated 2-deoxy-2-F18-fluoro-D-glucose (FDG) uptake of primary tumour is related to the likelihood of malignancy involvement in loco-regional lymph nodes (LNs) in 126 non-small-cell lung cancer (NSCLC) patients (M:F=103:23, age=65+/-9.7 years). Maximum standardised uptake values (maxSUV) and Glut-1 expression levels (determined by PET and immunostaining, respectively) of primary tumours and PET positive loco-regional LNs were compared. Significant correlations were found between malignant LNs and primary tumours with respect to maxSUV (r=0.6451, p<0.0001), %Glut-1 expression (r=0.8341, p<0.0001) and Glut-1 staining intensity (rho=0.827, p<0.0001). The area-under-curve value for LN differentiation using lymph node maxSUV was significantly higher in patients with a primary tumour maxSUV of >6 (AUC=0.775, p=0.0001). High correlations between the primary tumours and metastatic LNs in NSCLC with respect to the Glut-1 mediated FDG uptake may be useful for mediastinal LN discrimination by FDG-PET.