Background and Objectives: Natural killer T-cell lymphoma (NKTCL) and diffuse large B-cell lymphoma (DLBCL) are the two most prevalent subtypes of lymphoma in the sinonasal region. Accurately differentiating between sinonasal DLBCL and NKTCL is crucial for determining the appropriate treatment and prognosis. The present study compared the clinical characteristics of these two conditions. Methods: We conducted a retrospective review of 173 patients diagnosed with sinonasal lymphoma at a single institute between 2004 and 2017. This review included only patients with DLBCL and NKTCL who had more than 6 months of follow-up records. We analyzed patient data encompassing clinical characteristics, pathologic findings, radiologic findings, treatment modalities, recurrence, and survival. Results: Among the patients analyzed, 117 patients were diagnosed with NKTCL and 45 with DLBCL. Endoscopic evaluation revealed a significantly higher incidence of crusting (p<0.001) and necrotic lesions (p=0.001) in patients with NKTCL, whereas polypoid masses were more commonly observed in patients with DLBCL (p<0.001). Computed tomography (CT) scans indicated no significant differences in bilaterality or bone destruction between the two groups. The DLBCL group exhibited a higher rate of concurrent lymph node or organ involvement than the NKTCL group (p<0.001). The 5-year overall survival rate was 67.4% for DLBCL and 69.1% for NKTCL, with no significant difference between the two. Conclusion Clinical differences exist between sinonasal DLBCL and NKTCL in terms of endoscopic and CT findings. These distinct characteristics can aid in distinguishing between the two types of sinonasal lymphoma during clinical diagnosis.