 Only the cartilaginous part of the ET is accessible for treatment procedures. We also know that 20 of the patients dilated do not respond to dilation, and relapse of middle ear disease occurs 2. At present, no diagnostic procedure can distinguish between later responders and non-responders to dilation. Therefore, level diagnostics of obstruction and possibly identification of other discriminating parameters are important. Computer tomography CT is considered necessary before any type of tube intervention, mainly to exclude obstruction in the bony part of the tube or identification of any other pathoanatomical condition to contraindicate balloon dilatation. Visualisation of obstructions in the cartilaginous part is not possible with todays methods. Nor does the method provide any information on tube function. 