The cochlear implant (CI) has been indicated for children with severe and/or profound bilateral hearing loss who do not benefit from hearing aids and have adequate and motivated family for the use of the device, as well as adequate rehabilitation conditions at their hometowns. Currently, the demand for CI also occurs by deaf parents, fluent in Brazilian Sign Language (LIBRAS), who resort to this treatment to offer their children another reality. The environment of these children is bilingual, with exposition to LIBRAS through their parents and to oral language through close relatives, audiologist/speech-language pathologist, and the school. In this sense, the present study aimed to follow-up four implanted deaf children - two with deaf parents fluent in LIBRAS (exposed to a bilingual environment), and two with hearing parents (exposed to oral environment). For this purpose, abilities of hearing and oral language development were compared in these children with CI. It was observed that all four children in this study presented similar language development and auditory skills throughout the first year of CI use. However, after this period, children inserted into a bilingual environment had better auditory and linguistic performance when compared to the other children. Children in bilingual environments can benefit from the CI, developing auditory skills and oral language similarly to children inserted into an oral environment. It is emphasized that the benefits of the device is dependent on several factors, and further studies are needed.