Summary: In order to investigate the clinical significance of 99mTc-Tetrofosmin (TF) seintigraphy in the evaluation of lung cancer and mediastinal lymphoid node involvement, 33 patients with pulmonary neoplasmas were subjected to both 99mTc-TF scintigraphies and CT scans in one week before their operations or puncturations. All the images were judged visually and the emission images were analyzed with semi-quantitative methods in addition. The results of each group were compared. There was marked difference in target/non-target (T/N) ratio between the lung cancer group and the benign lesion group (P