Cochlear implantation (CI) has reached over years of practicing high standards of surgical outcomes. Even patients with significant residual hearing are nowadays benefiting from a cochlear implant. However, the speech perception still depends to great extent on the adequate pitch match between the frequency components delivered by an electrode array and individual cochlear tonotopic map. Compression, deletion or shift of frequency components can be tolerated by patients only to some extent. Furthermore, low frequency information delivered to the cochlear apex is particularly important for spatial hearing. It is therefore important to use the electrode array of an appropriate length for each individual cochlea. The large variability in the anatomy makes this task difficult as a single design does not fit all cochlear shapes. Fortunately, preoperative CT imaging, routinely taken in most of ENT clinics, can be exploited also for the prediction of the cochlear duct length (CDL). It turns out that a single radiological measurement, the diameter of the basal turn, is highly correlated with CDL and its measurement can be used for the informed selection of the most suitable electrode array length from the available array portfolio for each CI patient.