Background and Aims. Quercitrin (QR; quercetin-3-0-rhamnoside) has been used previously as an antibacterial agent and has been shown to inhibit the oxidation of low-density lipoproteins and prevent an allergic reaction. Furthermore, it was demonstrated that quercitrin exerts protective effects against H2O2-induced dysfunction in lung fibroblast cells. However, the mechanisms of quercitrin effects on cancer cell proliferation and apoptosis is not well understood. The aim of this study is to investigate the cytotoxic and apoptotic effects of quercitrin and the molecular mechanisms of quercitrin-induced apoptosis in non-small cell lung cancer (NSCLC) cell lines.