Bacterial biofilms are involved in many human bacterial infectious processes and in chronic rhinosinusitis as well. The aim of this study was to determine whether biofilm exists in nasal polyps, both in diffuse nasal polyposis (DNP) and antrochoanal polyps (ACP).Tissue samples were taken from seven patients suffering from DNP and three patients suffering from ACP, based on the defined patient inclusion and exclusion criteria. After the preparation, the tissue samples were analyzed by means of scanning electron microscopy (SEM) for signs of biofilm formation.Signs of biofilm presence were found in all DNP patients. In ACP cases, biofilm was found in the stalk and nasal, polypoid part of the ACP, whereas there were no signs of biofilm on diseased mucosa of the posterior wall of the maxillary sinus.Our preliminary study showed a possible role of bacterial biofilm in pathogenesis and maintenance of both DNP and ACP. There are no obvious differences in the SEM appearance of biofilms in DNP and ACP. Future research is needed to explain why biofilm is present in cases of diffuse nasal polyposis and at the nasal part of ACP, but not on the maxillary sinus part of ACP.