Craniofacial tomography of 55 patients with tumours of the nasal fossa and the paranasal sinuses were examined retrospectively. Only those tomograms were considered which had been taken before surgical or radiological treatment. The clinical classification of the tumours resulting from the tomographic findings shows, that these are, in most cases, advances tumours, which have already invaded neighbouring regions. Depending on their original site, the tumours will preferably spread in certain directions. In some cases, the opacity is not caused by the tumour itself, but by accompanying inflammations. The tomogram will always show up intra-operatively established tumourous bone destructions. However, the appearance of bony cortex on x-ray film without any clearly defined outline, may represent pseuodefects, especially when the adjacent tumour shadow is very dense or if the bony cortex is not situated approximately perpendicular to the tomographic level.