Abstract: Objective To discuss ⁹⁹Tc^m-methoxyisobutylisonitrile(⁹⁹Tc^m-MIBI)imaging evaluation of the value of chemotherapy in patients with non-small cell lung cancer(NSCLC).Methods Seventy-one patients with NSCLC were studied with ⁹⁹Tc^m-MIBI SPECT before chemotherapy.The patients were classified by a follow-up CT as good responders(complete or partial remission)and poor respenders(stable disease or progressive disease).Following injection vein administration of 740MBq ⁹⁹Tc^m-MIBI,SPECT imaging at 10-30 min(early)and 2-3 h(delayed)were performed.Regions of interests were placed over the tumors and contralateral normal tissue on one transverse section.The ⁹⁹Tc^m-MIBI uptake ratio of the lesion to that in the contralateral normal lung was obtained from early images(ER)as well as delayed images(DR).The retention index(RI)was measured as:RI=(DR-ER)/ER×100%. ⁹⁹Tc^m-MIBI tumor uptake parameters were compared with the chemotherapeutic response.Results ⁹⁹Tc^m-MIBI uptake was significantly higher in responders than in non-responders:2.39±0.21 vs 1.89±0.19 and 2.50±0.19 vs 2.05±0.21 for ER and DR,respectively(t=8.311,8.480,P<0.05).The median of RI in good response group was significantly higher than that in poor response group(6.63% vs 5.13%,Z=2.416,P<0.05).Conclusion ER,DR and RI of ⁹⁹Tc^m-MIBI SPECT may benefit to evaluating chemotherapy response NSCLC.