The main purpose of the series of three papers is to describe drugs, which are used in photodynamic therapy. Photodynamic therapy is a new approach towards the cancer treatment. The therapy uses three agents: light of an appropriate wavelength, photosensitizer and oxygen, which separately are inactive. When they interact singlet oxygen is generated. Singlet oxygen, which is one of the reactive oxygen species, can react with many components of the cell, including cell and intracellular membranes. This method is very promising because it may selectively act on tumor through irradiation of selected parts of the body or by nanotechnology to delivery photosensitizer. The article shows drugs, which are administered in practical care and in clinical tests.