Paranasal sinus lymphoma is an uncommon malignancy and is often difficult to diagnose. Early diagnosis is essential for effective treatment. The tumour generally has poor prognosis. Ophthalmological symptoms and signs occur early in the disease process due to the close proximity of the orbit to the paranasal sinuses. Common presenting features include eye pain, proptosis, visual loss and diplopia. We report a case of frontal sinus lymphoma that presented as a superior-nasal orbital mass in an 84 year old man. CT scan demonstrated a mass occupying the frontal sinuses, with destruction of the anterior bony wall of the frontal sinus and extending to the right orbit. Histology revealed diffuse large B cell non Hodgkin's lymphoma. The tumor was treated with radiotherapy and showed regression; however the patient died 9 months later. Sinus tumours are encountered by ophthalmologists and should be considered in patients presenting with an orbital mass.