The presenting symptoms of sinonasal lymphoma are usually similar to those of benign inflammatory diseases. Adequate amount of biopsy tissue is required for a definitive diagnosis because tumor coexisting with necrosis or inflammation is not uncommon. Therefore, the diagnosis of sinonasal lymphoma is a challenge for rhinologists. Thirty-two patients diagnosed as having sinonasal lymphoma from 1990 to 2010 in our hospital were included in this study. The presenting symptoms of these patients included nasal obstruction, rhinorrhea, bloody discharge/epistaxis, post nasal drip, facial swelling, neck mass, orbital symptoms, fever, and body weight loss. The average period between patients' awareness of their symptoms and their decision to seek medical help was 8.9 months. When they were referred to our hospital, the first impression of 20 patients (62.5%) was benign or malignant nasal neoplasm, and that of the other 12 patients (37.5%) was rhinitis or rhinosinusitis. These patients then received image studies and biopsy or surgical intervention. Most patients needed repeated biopsies, endoscopic sinus surgery, turbinectomy, or Caldwell-Luc operation for a definitive diagnosis. Their histopathologic classification included NK/T cell lymphoma (n = 13, 40.6%), peripheral T cell lymphoma (n = 12, 37.5%), and diffuse large B cell lymphoma (n = 7, 21.9%). Peripheral T cell lymphoma and NK/T cell lymphoma mostly occurred in the nasal cavity, whereas sinus involvement without nasal disease is common in B-cell lymphoma Our results reveal that patients with sinonasal NHL tend to ignore their symptoms until they become serious, and a definitive diagnosis usually requires repeat and deep biopsy.