Currently various methods are being tried to treat tumor tissue. One of treatment is the photodynamic therapy (PDT). It generates reactive oxygen species (ROS), which directly induces apoptosis or necrosis of tumors. Many studies focused on changes in mitochondria or internal signaling. But there was no comparison between tumor and normal cell membranes about ROS effect, even though they affect membranes1. Therefore, we studied the response to ROS using planar lipid bilayer and liposomes to determine their effect on cell membranes in the environment in which ROS are produced. In the ROS environment, it was affected by lipid bilayer containing unsaturated lipids. In the symmetrical tumor cell lipid+bilayer, it showed only unstable appearance and was not destroyed because of ROS. On the other hand, asymmetric lipid bilayer that mimics normal cells and only consist of unsaturated lipid bilayer were observed to have a membrane destroyed in the ROS environment. In liposomes experiment, the most leakage occurred from a mimicking of an asymmetrical normal cell. As a result, we observed that mimicked normal cell membranes were most affected by ROS, and mimicked tumor cell membranes are relatively less affected.