Introduction: Hearing impairment is the most common sensorial disorder. Deafness has several etiologies. It is important to investigate them, not only because some may lead to lower performance with a cochlear implant, but also to define preventive strategies. Objective: To determine deafness etiology among patients submitted to cochlear implantation. Methods: Retrospective sampling of patients submitted to cochlear implantation between 2006 and 2017 in a Brazilian referral hearing impairment center. Patients were grouped into post-lingual or pre-lingual deafness and an etiological profile was outlined for each group. Results: 159 patients were evaluated, 74 post-lingual and 85 prelingual. In post-lingual group, the most common cause of hearing impairment was meningitis (n = 16/21,62%). Other etiologies were: non-syndromic genetic hearing loss (n = 12/16,22%), otosclerosis (n = 7/9,46%), autoimmune (n = 5/6,76%), viral infections-mumps and measles (n = 3/4,05%), Alport syndrome (n = 2/2,7%), Meniиreґs disease (n = 2/2,7%), ototoxicity (n = 2/2,7%), enlarged vestibular aqueduct (n = 2/2,7%), otitis media complications (n = 2/2,7%), trauma (n = 2/2,7%), lues (n = 1/1,35%), vestibular schwannoma (n = 1/1,35%), stroke (n = 1/1,35%), auditory neuropathy (n = 1/1,35%) and 15 patients (20,27%) had undefined etiology. In pre-lingual group, non-syndromic genetic hearing loss was the most prevalent cause (n = 22/25,88%), followed by perinatal complications (n = 20/23,53%), congenital infections-cytomegalovirus, rubella and mumps (n = 8/9,41%), genetic syndromes such as Waardenburg (n = 5/5,88%), meningitis (n = 5/5,88%), malformation-mostly incomplete partition type II (n = 3/3,53%), auditory neuropathy (n = 3/3,53%), ototoxicity (n = 2/2,35%) and 17 patients had undefined causes (20%). Conclusion: In our population, the most frequent etiology for postlingual deafness was meningitis and for pre-lingual deafness was non-syndromic genetic causes.