Background: The aim of this study was to evaluate the disease outcomes of patients treated with definitive and adjuvant radiotherapy for squamous cell carcinomas of the nasal cavity and paranasal sinuses in a single institution.Methods: Between 2007-2012 patients were retrospectively identified from electronic databases who had undergone surgery and adjuvant radiotherapy or definitive radiotherapy for sinonasal squamous cell carcinomas with curative intent.Results: Fourty three patients with sinonasal squamous cell carcinoma were identified (22 nasal cavity, 21 paranasal sinuses). 31/43 (72%) had T3 or T4 disease; nodal stage was N0 in 38, N1 in 4, Na/b in 0 and N2c in 1 patient. Median age was 67 years (range 41-86). 18 (42%) received definitive and 25 (58%) adjuvant radiotherapy. Radiotherapy was delivered using either conventional radiotherapy (n = 39) or intensity modulated radiotherapy (n = 4). Elective neck radiotherapy was delivered to two patients. Chemotherapy was delivered to 6/43 (14%) of patients. Two-year local control, regional control, distant metastases free survival, progression free survival, cause specific survival and overall survival were 81%, 90%, 95%, 71%, 84% and 80% respectively. There was no significant difference in outcome comparing patients who underwent surgery and adjuvant radiotherapy with patients receiving definitive radiotherapy (2 year locoregional disease free survival 75% and 70% respectively, p = 0.98). Pooly differentiated tumours were significantly associated with inferior disease outcomes. Local, regional, combined local and regional, and distant failure occurred in 7 (16%), 3 (7%), 1 (2%) and 2 (5%) of patients; all 3 regional recurrences were in patients with nasal cavity squamous cell carcinomas who had not undergone elective neck treatment.Conclusions: Definitive or adjuvant radiotherapy provides an effective treatment for sinonasal malignancies. The main pattern of failure remains local, suggesting the need for investigation of intensified local therapy. Whilst remaining uncommon, the cases of regional failure mean that the merits of elective lymph node treatment should be considered on an individual basis.