In vitro studies have shown that technetium-99m methoxyisobutylisonitrile (Tc-99m MIBI) is a transport substrate for the P-glycoprotein (Pgp) pump. Therefore, Tc-99m MIBI uptake of tumors can be used to predict chemotherapy response in lung cancers. However, whether lung resistance-related protein (LRP) expression affects tumor accumulation and efflux of Tc-99m MIBI in lung cancers is not known. Our aim was to use Tc-99m MIBI uptake of tumors to predict Taxol based chemotherapy response of advanced non-small cell lung cancer (NSCLC) and to compare Pgp or LRP expression. Before chemotherapy with Taxol, 30 patients with stage IIIb or IV NSCLC were enrolled in this study. Chemotherapy response was evaluated in the third month after completion of treatment by clinical and radiological methods. No significant differences were found for other prognostic factors (age, sex, body weight loss, performance status, tumor cell type, and tumor stage) between the 15 patients with good response and the other 15 patients with poor response. Early chest single photon emission computed tomography (SPECT) was performed 10 min after intravenous injection of Tc-99m MIBI. Early tumor-to-normal lung (T/L) uptake ratios were calculated quantitatively on Tc-99m MIBI chest SPECT images. Immunohistochemical analyses were performed on multiple nonconsecutive sections of the biopsy specimens to determine Pgp and LRP expressions. The T/L uptake ratios on early Tc-99m MIBI chest SPECT images of 15 patients with good response were significantly higher than those of the other 15 patients with poor response. Significantly higher T/L uptake ratios were found in patients with negative than positive Pgp expression (p<0.05). However, no significant differences of T/L uptake ratios were found between patients with negative and positive LRP expressions (p>0.05). We concluded that Tc-99m MIBI chest SPECT could accurately predict Taxol base chemotherapy response of patients with advanced NSCLC. In addition, The Tc-99m MIBI tumor uptake was related to Pgp but not LPR expression in NSCLC.