Green tea is one of most popular traditional teas in korea. ``The purpose of this study was comparing the effects of ethanol extracts on three kinds of cancer cell lines(HepG2, A549, EATC) according to its concentration and exposure time. For this purpose, we obseπed morphological changes under inverted and electron microscope and anallysed cytotoxicity . EATC(Ehrlich-Lettre Ascites Tumor Cell) cells were damaged by 100μg/m1 ethanol extracts treatment until 72 hours gradually. In A549 cells, ethanol extracts caused severe cellular injury abrupt1y and lasted for 72 hours. However, cellular necrosis and growth inhibition in both of them could not be observed in 1, 10μg/ml ethanol extracts administration. Whereas, the effects of that were weak in all of concentrations and exposure times in HepG2 cells. In conclusion, green tea ethan이 extracts induced strong inhibition of growth and severe cellular damages in A549(Lung Cancer) and EATC except HepG2(Hepatoblastoma). In addition, its effects were dependent on concentration and duration of ethanol extracts. Therefore, though there were some different effect according to cancer type, it suggested that green tea would be helpful to prevent carcinogenesis and treat cancer.