Planar scan and single photon emission CT (SPECT) findings using Ga-67 and Tl-201 were compared with Pathological findings after thoracotomy in 23 patients with proven primary lung cancer. The stage was pT1NO in 9 cases, pT2NO in 5 cases, pT2N1 in 2 cases, pT2N2 in 1 cases, pT3NO in 1 cases, pT3N1 in 2 cases, pT3NO in 3 cases. The patients were injected 6mCi of Tl-201, planar images were taken at 15 minutes, SPECT images were taken at 1 hour. Ga-67 planar scan and SPECT were performed 48-72 hours after intravenous administration of 3mCi of Ga-67. When accumulations of these radiopharmaceuticals was noted in the primary lesion, hilar and mediastinal regions, the results were considered to be positive. The sensitivity of primary lesion detection was 33% with planar Ga-67 scintigraphy, 50% with Ga-67 SPECT, and 68% with planar T1-201 scintigraphy, 100% with Tl-201 SPECT. For detection of hilar nodal involvement, Ga-67 SPECT had 100% sensitivity and 31% specificity, and Tl-201 SPECT had 86% sensitivity and 100% specificity. In mediastinal staging, Ga-67 SPECT had 100% sensitivity and 31% specificity, and Tl-201 SPECT had 100% sensitivity and 88% specificity. For evaluation of the primary lesion and lymph node metastasis, Tl-201 SPECT proved superior to Tl-201 planar scan, Ga-67 planar scan and Ga-67 SPECT.