We report on the use of magnetic resonance tomography for tumours of the paranasal sinuses. The value of gadolinium-DTPA was investigated in a prospective study. For tissue characterisation and determination of the extent of the disease, combined use of T2-weighted multi-echo sequences and plain and contrast examinations with T1-weighted spin-echo sequences are superior to CT. CT must be used, however, to demonstrate bone changes. Endocranial tumour extension can be demonstrated more precisely with magnetic resonance than with CT.