In 13 patients presenting as lethal midline granuloma (LMG), computed tomography proved essential for determining the extent of the disease, guiding biopsy and planning radiotherapy. Magnetic resonance imaging (MRI) was also helpful for the latter, because it could distinguish fluid retained within the paranasal sinuses from solid masses and tumour from granulation tissue; it was of little value for detecting bone lysis. Eight of the 13 patients proved to have T-cell lymphoma, two had Crohn's disease, in one the lesion was factitious and two had granulomas without diagnostic histological features.