The cancer stem cell (CSC) theory is currently a very important field in cancer research. This theory states that tumours are organised in a hierarchical manner with a subpopulation of limited number called CSCs with the ability to self-renew and undergo asymmetrical divisions, giving rise to a differentiated progeny that represents most of the tumour populations. CSCs are metastatic and chemoresistant, two features that very likely contribute to the poor response of locally advanced lung cancer. CSCs have been identified in non-small-cell lung cancer cell lines as well as those from patient primary samples. A correlation has been found in terms of chemoresistance and bad prognosis in patient-derived samples enriched with CSCs, indicating that these cells are an important target for future therapy combinations. Therefore, understanding the biology and exploring cell markers and signalling pathways specific for CSCs of lung cancer may help in achieving progress in the treatment of the disease.