OBJECTIVE: To compare kinetics and accumulation of 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (FDG) in primary lung cancer between diabetic and non-diabetic patients using positron emission tomography (PET).METHODS: Five diabetic patients and 21 non-diabetic patients underwent dynamic FDG-PET to image untreated primary lung cancers. Standardized uptake value normalized for lean body mass (SUL) was determined in tumor, blood, muscle, and lung. A 3-compartment metabolic model was applied to FDG kinetics in tumors in 24 of 26 patients.RESULTS: At the time of PET scans, serum glucose levels were elevated in 5 diabetic patients, while 21 non-diabetic patients showed normal glucose levels. In diabetic patients, tumor SUL, tumor/blood and tumor/muscle SUL ratios were significantly decreased (P < 0.02) and also tumor/lung SUL ratio declined (P = 0.064), as compared to non-diabetic patients. In addition, the rate constant for FDG phosphorylation (k3) and influx constant (Ki) in diabetic patients were significantly lower than those in non-diabetic patients (P < 0.02).CONCLUSION: In diabetic patients, the rate of FDG accumulation in tumors is decreased, and tumor targeting with FDG is impaired. Diabetes may reduce the sensitivity of FDG-PET for lung cancer detection.