The aim of the study was to observe, using scanning electron microscopy (SEM), the ratio of bacterial biofilm coverage of adenoidal tissue in children diagnosed with chronic rhinosinusitis (CR), compared to the ratio of adenoid bacterial biofilm coverage in children diagnosed with obstructive sleep apnea (OSA). We also performed histopathological and immunohistochemical tests to correlate the results with the images obtained from SEM. We estimated, using an image analysis program, the coverage ratio with bacterial biofilm on the surface of the lymphatic tissue. Adenoid vegetation extracted from children with CR had a higher percentage of bacterial biofilm coverage compared to the group diagnosed with OSA. In the nasopharynx of children with CR, the bacterial biofilm had a constant role of infection generator, and adenoidectomy was the only effective therapeutic procedure to relieve the symptoms. Allergy tests were performed in all children to establish a link between CR, OSA and allergic rhinitis.