Tumor imaging with myocardial perfusion agents has been a focal point for researchers. A kinetic study with 99m Technetium- methoxyisobutylisonitrile ( 99m Tc-MIBI) was performed to evaluate the tumor uptake of this radiopharmaceutical in lung cancer. Thirty-five patients with lung cancer were studied. In 21 (60%) patients, there were regions of high uptake of 99m Tc-MIBI in the lesions. Heart/tumor (H/T), heart/lung (H/L) and tumor/lung (T/L) ratios were obtained. H/T and H/L ratios were 1.66±0.22 and 2.10±0.28 in 2-3 min, and 1.69±0.25 and 2.14±0.27 in 29-30 min respectively. The T/L ratio was 1.28±0.10 in 2-3 min and 1.29±0.14 in 29-30 min. While the differences between H/T and H/L ratios were statistically significant, there were no significant differences between early and late uptake ratios. Seventy per cent (7/10) of small cell and 56% (14/25) of squamous cell cancers were detected visually. 99m Tc-MIBI uptake in small cell tumors was higher than in squamous cell tumors. Tumor blood flow was seen in the systemic phase of the radiopharmaceutical as the blood supply of the tumor was the bronchial artery. The sensitivity of 99m Tc-MIBI planar scintigraphy for lung cancer detection was inadequate, and the early and delayed ratios revealed that small cell cancer showed higher 99m Tc-MIBI accumulation than squamous cell cancer.