Objectives: This study aimed at testing preoperative factors that can affect the postoperative performance after cochlear implantation. It also aimed at determining the relationship between the Electrically Evoked Compound Action Potential (ECAP) and postoperative performance in Nucleus CI24 users, and testing the value of these electrophysiological measures, in reflecting the underlying extent of pathological damage and residual neural survival, reflected by short duration of hearing loss and better preoperative speech recognition ability. Design: sixty cochlear implant patients with postlingual severe-to-profound hearing loss who were at least eighteen years old, were included in this study. Seven were bilaterally implanted, giving a total of sixty seven ears. Their preoperative duration of deafness and sentence recognition scores were obtained. Patients were subjected to three to six months postoperative word recognition test (CNC). ECAP growth functions were recorded and psychophysical mapping was completed. Two years later, ECAP recovery functions were collected. Results: The study showed that the predictive index based on the duration of deafness and preoperative speech recognition is substantially efficient in predicting the postoperative monosyllabic word recognition. ECAP growth and recovery functions are related to preoperative duration of deafness, and sentence recognition, the same factors which proved to be important for predicting postoperative speech perception. ECAP measures are also related to, and can predict patient’s behavioral map. However, none of the ECAP measures were directly correlated with postoperative word recognition ability. Conclusions: Electrically evoked compound action potential (ECAP) growth, and recovery functions provide an objective measure that correlates with the patient’s preoperative residual hearing and underlying neural status. They can also assist in predicting the behavioral map. However, this study found no relationship between postoperative performance on word recognition tests, and ECAP growth functions, or recovery functions.