We report about 3 patients with a Arachnoidal Cyst in the internal acoustic meatus. The first patient had a cyst deriving from the Falloppian Canal fundus into the cochlea reaching the internal carotic artery. The second cyst we found followed the widened Falloppian canal from the internal acoustic meatus to the region of the oval window with disturbance of the ossicular chain function. The third patient had a Arachnoidal Cyst in the borders of a enlarged internal acoustic meatus. We describe the history and the anatomic situation of the three patients.