Tetrapyrrolic compounds such as porphyrins and metalloporphyrins are highly interesting for pharmaceutical chemistry designs considering their good biocompatibility and therapeutic potential. The aim of the present work was a preliminary in vitro evaluation of some unsymmetrical porphyrins and the corresponding symmetrical structures, as potential candidates for the photodynamic therapy of malignant tumors. The biocompatibility of these compounds was assessed in terms of their in vitro effect on the viability and proliferation of breast human carcinoma MCF-7 cells and human normal peripheral blood mononuclear cells (PBMCs). Results indicated that the asymmetric and symmetric porphyrins were non-toxic against tumor MCF-7 cells and PBMCs in the concentration range 0.2 – 2 µM, making them valuable candidates for further development as photosensitizers for PDT in tumors. Moreover, asymmetric compounds tended to restore the response of normal and tumor cells affected by the vehicle used for the initial solubilization of porphyrins (DMSO), while the symmetric compounds were less active in this respect.