A modern and non-invasive approach in the treatment of tumors, where the proper introduction of photosensitizers (PS) into cells is followed by irradiation of the local area with visible light, is called photodynamic therapy (PDT). Porphyrin, as PS, can efficiently absorb visible light and stimulate the formation of reactive oxygen species (ROS) that will induce cell apoptosis in situ. PDT includes non-toxic components of PS, light of an appropriate wavelength (600-800 nm) and oxygen required for a successful treatment outcome. The specific purpose of this study was to examine the efficacy of the photodynamic effect of N-oxidized pyridylporphyrins conjugated to lipophilic chains of varied lengths on melanoma cells under hypoxic conditions. The cytotoxic effects of the compounds on fibroblast (HFF) and melanoma (MEWO) cells under normal and reduced oxygen concentration conditions (hypoxic conditions) were first determined. We equally determined whether porphyrins enter melanoma cells and determined the key part of the cell where they accumulate the most. Based on the results of treatment of human cells HFF and MEWO with compounds 10C-O, 14C-O, 18C-O and AMIDO-O, we proved that these compounds are not cytotoxic in the dark. Compounds 10C-O and AMIDO-O do not cause cytotoxic effects in either lower or higher concentrations. The lipophilicity of the compounds affected cell entry and cytotoxicity levels. Compounds with a longer alkyl chain (14C-O and 18C-O) have been shown to be more lipophilic and of stronger red color under a fluorescent microscope because they enter cells more easily and typically cause cell death. These compounds inhibit the growth of MEWO and HFF cells and under conditions of hypoxia, achieved by treatment with CoCl2, showed to be more selective for melanoma cells than for normal fibroblasts. These results support the need for further research to reveal the exact mechanisms of action of the compounds for the most effective treatment that will utilize tumor hypoxia as a treatment advantage, providing a potential and promising effect in the treatment of resistant hypoxic tumors.