목적: The straight arrays with circumferential electrodes are widely used in severely malformed cochlea. However, the unpredictability of the location of residual spiral ganglion neurons in such malformations argues against obligatorily pursuing the full-banded electrode in all cases. Here, we present an experience of electrically evoked compound action potential(ECAP) and radiography based selection of an appropriate electrode for severely malformed cochlea. 방법:Three patients with the severely malformed cochlea, showing cochlear hypoplasia type II, incomplete partition type I, and cochlear aplasia with a dilated vestibule(CADV), were included, and the cochlear nerve deficiency(CND) was evaluated. Full-banded electrode (CI24RE(ST)) and slim modiolar electrode(CI632) were alternately inserted to compare ECAP responses and electrode position. 결과:In patient1(CH-II with CND) who had initially undergone cochlear implantation(CI) using the lateral wall electrode(CI422), a revision CI was performed due to incomplete insertion of CI422 and resultant unsatisfactory performance, thus explanting the CI422 and re-inserting the CI24RE(ST) and CI632 sequentially. Although both electrodes elicited reliable ECAP responses with correct positioning, CI24RE(ST) showed overall lower ECAP thresholds compared to CI632; thus, CI24RE(ST) was selected. In patient2(IP-I with CND), CI632 elicited superior ECAP responses relative to CI24RE(ST), with correct positioning of the electrode; CI632 was chosen. In patient3(CADV), CI632 did not elicit an ECAP response while meaningful ECAP responses were obtained with the CI24RE(ST) array once correct positioning was achieved. All patients markedly improved auditory performance postoperatively. 결론:ECAP and radiography-based strategy for an appropriate electrode may be useful for severely malformed cochlea, leading to enhanced functional outcomes. Additionally, the practice of sticking to the full-banded straight electrode may not always be the best for IP-I and CH-II.