The effect of gefitinib on advanced non-small cell lung cancer (NSCLC) was various. How to choose the sensitive patients and improve the effect was difficulty in clinic. This study was to assess the correlation of epidermal growth factor receptor (EGFR) mutations and HER2/3 protein expression with the effect of gefitinib on Chinese patients with advanced NSCLC.From May 2002 to February 2005, a total of 106 Chinese NSCLC patients who had failed at least one chemotherapy regimen were treated with gefitinib 250 mg once a day. The mutations in the exons 18-24 of EGFR gene were detected in the tumor tissues from 106 patients before the treatment of gefitinib, and HER2/3 expression in 84 tumor samples were detected by immunohistochemistry.Mutation was identified in 32 (30.2%) tumor tissues. Overall remission rate was significantly higher in the HER2 high expression patients than in the HER2 low expression patients (36.8% vs 17.4%, P=0.044). HER2 and HER3 expression levels were not associated with time to progression (TTP) and overall survival (OS). The patients with HER2/3 single high expression had relatively longer TTP and OS than those with HER2/3 single low expression (6.1 vs 9.1 months, P=0.725; 6.1 vs 9.0 months, P=0.862), while those with concomitant HER2/3 high expression had significant longer TTP and OS. EGFR-mutated patients with HER2 expression or high HER2 and HER3 expressions were more sensitive to gefitinib.EGFR mutations combined with HER2/3 expressions is a significant predictor for gefitinib efficacy on Chinese patients with advanced NSCLC.