Objective To investigate the role of three-dimensional (3D) radiotherapy to the thoracic primary tumor in non-small cell lung cancer (NSCLC) patients with bone metastases during chemotherapy with concurrent 3D radiotherapy. Methods From 2003 to 2010, the clinical data of 95 stage Ⅳ NSCLC patients with bone metastases were collected. All patients received 3D radiotherapy to the thoracic primary tumor and at least 2 cycles of chemotherapy. Of the 95 patients, 47 had only bone metastases, and 48 had metastases to bones and other organs. The Kaplan-Meier method was used to calculate overall survival (OS) rates. The log-rank test was used for survival difference analysis and univariate prognostic analysis. The Cox regression model was used for multivariate prognostic analysis. Results The follow-up rate was 95%. The 1-, 2-, and 3-year OS rates were 44%, 17%, and 9%, respectively. The univariate analysis showed that radiation dose to the planning target volume (PTV) of primary tumor of ≥63 Gy, response to treatment of primary tumor, and at least 4 cycles of chemotherapy were favorable prognostic factors for OS in all patients (P=0.001, 0.037, and 0.009). Radiation dose to the PTV of primary tumor of ≥63 Gy remained the favorable prognostic factor for OS in patients with only bone metastases and those with metastases to bones and other organs (P=0.045 and 0.012). Among patients with only bone metastases, those with T₁+T₂ primary tumors had longer OS than those with T₃+T₄ primary tumors (P=0.048). The multivariate analysis showed that radiation dose to the PTV of primary tumor of ≥63 Gy and metastases to bones only were independent favorable prognostic factors for OS in all patients (P=0.036 and 0.035). Conclusions For NSCLC patients with bone metastases, 3D radiotherapy to the thoracic primary tumor and its dose play an important role in improving OS during chemotherapy with concurrent 3D radiotherapy.