Purpose <p>Nasal associated lymphoid tissue (NALT) consisting of intraepithelial lymphocytes (IELs) and subepithelial lymphoid tissue has been scarcely studied. We aimed to compare the distribution of NALT in sinonasal polyps (cases) and normal nasal mucosa (controls).</p> Methods <p>We performed a preliminary, observational study of the distribution of subepithelial lymphoid follicles in 10 cases of sinonasal polyps and 10 normal controls. We also performed a count of CD4+, CD8 + and CD20 + IELs and CD34 + high endothelial venules (HEVs) using hemotoxylin and eosin staining and immunohistochemistry in both groups.</p> Results <p>The total area of both lymphatic follicle aggregates and organized lymphatic follicles in the lamina propria were significantly higher in cases than in controls (<i>p</i> &lt; 0.001). CD4 + helper and CD8 + T cytotoxic IELs were identified in the epithelium of both controls and cases. The overall number of CD8 + IELs was significantly higher than the number of CD4 + IELs among both cases (<i>p</i> &lt; 0.002) and controls (<i>p</i> &lt; 0.002). CD4 + IEL count was significantly higher among cases than controls (<i>p</i> &lt; 0.001), however. CD20 + IELs were absent in normal nasal mucosa but were seen in 3 cases of sinonasal polyp. The number of CD4 + follicular lymphocytes was also significantly higher in cases than controls (<i>p</i> = 0.005). Abundant HEVs were noted within the organized follicles and in the parafollicular region in both controls and cases.</p> Conclusion <p>NALT, specifically lamina propria lymphatic follicles, and CD4+, CD8 + and CD20 + IELs, play an important role in mounting an inflammatory response in sinonasal polyposis.</p>