PURPOSE: To ascertain the biologic significance of lung cancer Side population (SP) cells, which represent putative cancer stem cells (CSC) in the absence of consensus biomarkers for tumor-specific CSC. MATERIALS AND METHODS: We sorted and analyzed the angiogenic features of SP cells, isolated from tumor cell lines based on the exclusion of the DNA dye Hoechst 33342, from the NSCLC cell lines A549 and H460. RESULTS: Compared with non-SP cells, mRNA of vascular endothelial growth factor (VEGF)-A, VEGF-B, angiopoietin (ang)-1, ang-2, fibroblast growth factor-2 (FGF-2), cyclooxygenase-2 (Cox-2) and interleukin-8 (IL-8) were over-expressed in SP cells accompanied by over-expression of ABCG2 and MDR1 mRNA. The supernatant of cultured SP cells could significantly induce migration of human umbilical vein endothelial cells, while recombinant human endostatin (Endostar 25(®)) could inhibit the migration. CONCLUSIONS: This study revealed that the NSCLC SP cells might represent CSCs and possess pro-angiogenic properties, and antiangiogenesis represent a potential therapy.