The ability of bacteria and fungi to form biofilms, sessile communities of microorganisms responsible for the pathogenesis of many chronic and persistent infections, increases their hardiness to external conditions and contributes to the development of resistance to conventional antimicrobial agents. Given the alarming situation in the field of treating infections caused by pathogens that have developed antimicrobial resistance, there is a growing need for discoveries of new treatment methods. One of the possible approaches to treatment of infections caused by microorganisms in biofilm is the use of photodynamic inactivation. Photodynamic inactivation of microorganisms has a non-specific mechanism of action, based on the interaction of non-toxic photosensitizers, visible light and molecular oxygen, resulting in the generation of cytotoxic reactive oxygen species and singlet oxygen. Most photosensitizers are based on the tetrapyrrolic structure, with a high prevalence on the use of porphyrins. Some porphyrin compounds, such as porfimer sodium and endogenous protoporphyrin IX, are already being used as photosensitizers in the therapy of some cancers, and their potential for inactivation of microorganisms in biofilm is under investigation. Both photosensitizers have caused significant inactivation of the tested biofilms. Other photosensitizers are still in the experimental stage and their activity has not yet been sufficiently studied. Despite the significant inactivation achieved in planktonic microorganisms, tetracationic 5,10,15,20-tetra-(N-methylpyridinium-4-yl) porphyrin tetra-(p-toluenesulfonate) did not achieve satisfactory efficacy in most of the biofilms studied. Dicationic 5,15-bis-[4-(3-trimethylammonio-propyloxy) phenyl]porphyrin dichloride has shown to be an efficient photosensitizer in the inactivation of fungal biofilms but there is still no research on its efficacy in biofilms of bacterial origin.