Abstract: Objective: To investigate the relationship between the degree of ^99mTc-methoxy-isobutylisonitrile (MIBI) uptake and the expression of multidrug-resistant protein P-gp, MRP and GSTπin patients with primary lung cancer. Methods: Twenty-six patients with untreated primary lung cancer were studied prospectively. After i.v. administration of 925 MBq ^99mTc- MIBI, planar and SPECT imag-ing at 15 minutes and 120 minutes were performed. By means of semiquantitative method, T e / N, T d / N(tumor-to-normal lung ratio in early and delay image respectively) and RI% (retention indices) werecalculated. Immunohistochemical analysis was used to evaluate the expression of Pgp, MRP and GSTπ .Results: The positive rate of ^99mTc- MIBI in the patients with primary lung cancer was 92.31% and the mean value of T e / N, T d / N and RI% were 1.71± 0.44, 1.76± 0.41 and 4.58± 14.19 respectively. The posi-tive expression rates of P-gp, MRP and GSTπwere 75.00%, 58.33% and 45.83%. There was no signif-icant difference among them (x²=4.273,P=0.118). The positive co-expression rates of P-gp+MRP, P-gp+GSTπ, MRP+GSTπand P-gp+MRP +GSTπ were 41.67%, 37.50%, 29.17% and 20.83%. The RI%of P-gp positive group was significant lower than that of negative group (t=- 2.258, P=0.034). Conclu-sion: The study suggests that ^99mTc-MIBI scintigraphy may predict the MDR development associated with P-gp expression in lung cancer, which can offer theoretical basis for individual therapy.