Photodynamic therapy (PDT) is a clinical approach that uses light-activated drugs for the treatment of different kind of tumor tissues. HeLa tumor cells, as an experimental model for studying the new biomedical concept of associated PDT with 5, 10, 15, 20 -sulphonato-phenyl-porphyrin (TSPP) and an antitumor agent - cisplatin (CisPt), yielded to an enhanced effect on the suppression of tumor cells in vitro. The ultra structure changes of cells caused by the action of the new concept and laser irradiation were analyzed, putting into evidence linear survival curves, by the linear quadratic model.