BERNAL, Sarah Carolina. Hearing performance comparison between unilateral and bilateral cochlear implant users. 2019. Master thesis. Postgraduate program of rehabilitation and functional performance, RIBEIRÃO PRETO MEDICAL SCHOOL, UNIVERSITY OF SÃO PAULO. INTRODUCTION: Unilateral cochlear implant (CI) is more affordable, but presents low speech recognition and sound localization in noisy environments; on the other hand, bilateral CI demonstrates better results in speech perception and sound localization, but has higher cost and higher risks, making its benefits questionable. New studies are needed to compare both options in challenging conditions. OBJECTIVES: To evaluate adult users of unilateral and bilateral CI on speech perception in two azimuthal angles, in quiet and in ipsi and contralateral noise; to evaluate sound localization ability in four angles; to evaluate self-perception of difficulties with the CI and the ability to locate sounds on a daily basis. METHODOLOGY: The study included 60 subjects of both sexes, between 18 and 59 years, divided into 3 groups: GUunilateral CI (n=20), GBILbilateral CI (n=20), GCcontrol (n=20). Speech perception was assessed through a sentence recognition test, at 65 dB, in quiet and in noise (Speech Shaped Noise), S/N ratio of +5 dB and 0 dB. Sound localization was evaluated with two stimuli: a warble tone and the /ba/ syllable at 65 dB and 1500 Hz in four azimuthal angles. Self-perception was assessed through the APHAB questionnaire, only in the condition "with CI", as well as the Sound Localization Ability Questionnaire. RESULTS: There was difference between GUxGBIL in sound localization, APHAB, Localization Ability Questionnaire and IPRSR for all conditions, but S/N 0 dB. CONCLUSION: GBIL is the closest group to GC. Bilateral implantation showed higher performance compared to unilateral implantation.