This study was conducted to assess the feasibility of using Tc-99m labelled 2-methoxy isobutyl isonitrile (MIBI) scintigraphy, to evaluate benign and malignant intratoracic lesions and to assess the value in the differential diagnosis. The eligible population of the study included randomly selected 37 patients examined in Kocaeli University Pulmonary Clinic (19 men, 18 women) who had a abnormality in the PA chest X-ray and hadn't received any therapy. After intravenous injection of 15-25 mCi Tc-99m MIBI, early (10 minutes) and delayed (2.5 hours) static spot images of posterior and anterior thorax and SPECT images were obtained. Assessment of MIBI uptake was done visually. Of the 18 patients with primary bronchial carcinoma, increased abnormal uptake of MIBI corresponding to the location of lesion was reported in 14 patients with planar imaging and in 15 patients with SPECT and was considered positive. Three patients had no abnormal activity. Of the 19 patients with benign lesions, four had abnormally increased uptake of MIBI. In the detection of malignant lesions Tc-99m MIBI has 83.3%, 78.9%, 78.9%, and 83.3%, specificity, sensitivity, positive predictive value and negative predictive value respectively. Tc-99m MIBI tumor scintigraphy might be a valuable non-invasive method in the differential diagnosis of malignant and benign lung lesions. However further study with larger series for the relatively low sensitivity and specificity.