Temporal bone high resolution computed tomogram(TBHRCT) is a essential diagnostic tool in considering for cochlear implantation in patients with profound sensorineural hearing loss. This study was designed for an effort to provide an efficacy of TBHRCT in determination of inner ear malformations for the patients who have profound sensorineural hearing loss and to examine the relationships for the patients who have profound sensorineural hearing loss and to examine the relationships between TBHRCT findings and other preoperative evaluations for cochlear implantation in that patients. Authors examined 68 deaf patients to provide fundamental data for cochlear implantation. Inner ear abnormalities were founded in 13(19%) patients, among which 10(14.7%) patients had Mondini dysplasia in which 5 patients were hypoplastic type and 5 patients were hydrops type. Other inner ear abnormalities were as follows : lateral semicircular canal hypoplasia ; internal auditory canal abnormality ; cochlear aqueduct widening ; vestibular aqueduct widening. No relationships were found between TBHRCT finding and other test results : promontory test, K-WISC cognitive test etc.