Objective: To evaluate interindividual anatomical variations of the epitympanum and the usable space for implantation of active middle ear implants (AMEI) as well as the usefulness of a tablet-based software to assess individual anatomy on computed tomography (CT) scans. Patients: CT scans of 126 patients, scheduled for cochlea implantation (50.8% men; 0.6-90.0 yr) without middle ear malformations or previous middle ear surgery and with slice thickness 0.7 mm were analyzed. Main Outcome Measures: Since no standardized measurements to assess the size of the epitympanum are available, relevant distances were defined according to anatomical landmarks. Three independent raters measured these distances using a tablet-based software. Interrater correlation was computed to evaluate the quality of the measurement process. Descriptive data were analyzed for validation and for evaluation of interindividual anatomical variations. Influence of age and sex on the taken measurements was assessed.