A cochlear implant (CI) is a partially implanted electronic device that can help to provide a sense of sound and support speech to severely to profoundly hearing impaired patients. It is constituted by an external portion, that usually sits behind the ear and an internal portion surgically placed under the skin. The external components include a microphone connected to a speech processor that selects and arranges sounds pucked up by the microphone. This is connected to a transmitter coil, worn on the side of the head, which transmits data to an internal receiver coil placed under the skin. The received data are delivered to an array of electrodes that are surgically implanted within the cochlea. The primary neural targets of the electrodes are the spiral ganglion cells which innervate fibers of the auditory nerve. When the electrodes are activated by the signal, they send a current along the auditory nerve and auditory pathways to the auditory cortex. Children and adults who are profoundly or severely hearing impaired can be fitted with cochlear implants. According to the Food and Drug Administration, approximately 188,000 people worldwide have received implants. In Italy it is extimated that there are about 6-7000 implanted patients, with an average of 700 CI surgeries per year. Cochlear implantation, followed by intensive postimplantation speech therapy, can help young children to acquire speech, language, and social skills. Early implantation provides exposure to sounds that can be helpful during the critical period when children learn speech and language skills. In 2000, the Food and Drug Administration lowered the age of eligibility to 12 months for one type of CI. With regard to the results after cochlear implantation in relation to early implantation, better linguistic results are reported in children implanted before 12 months of life, even if no sufficient data exist regarding the relation between this advantage and the duration of implant use and how long this advantage persists in the subsequent years. With regard to cochlear implantation in children older than 12 months the studies show better hearing and linguistic results in children implanted at earlier ages. A sensitive period under 24-36 months has been identified over which cochlear implantation is reported to be less effective in terms of improvement in speech and hearing results. With regard to clinical effectiveness of bilateral cochlear implantation, greater benefits from bilateral implants compared to monolateral ones when assessing hearing in quiet and in noise and in sound localization abilities are reported to be present in both case of simultaneous or sequential bilateral implantation. However, with regard to the delay between the surgeries in sequential bilateral implantation, although benefit is reported to be present even after very long delays, on average long delays between surgeries seems to negatively affect the outcome with the second implant. With regard to benefits after cochlear implantation in children with multiple disabilities, benefits in terms of speech perception and communication as well as in quality of the daily life are reported even if benefits are slower and lower in comparison to those generally attained by implanted children without additional disabilities. Regarding the costs/efficacy ratio, the CI is expensive, in particular because of the cost of the high technological device, long life support, but even if healthcare costs are high, the savings in terms of indirect costs and quality of life are important. The CI, in fact, has a positive impact in terms of quality of life.