Title: HEARING RECOGNITION COMPARISON BETWEEN AIDED AND UNAIDED EAR IN HEARING AID USERS Objectives: The main goal of the present study is to investigate the difference of hearing recognition between the aided and unaided ear in long-term (>5 years) single-sided hearing aid users with moderate and severe hearing loss. Subjects and methods: In our study we observed 48 subjects with bilateral hearing loss > 40 dB, 31 males and 17 females. All subjects were unilateral hearing aid users for at least 5 years. This retrospective study was carried out from January 2018 until June 2018 at the Department of Otorhinolaryngology & Head and Neck Surgery, University Hospital of Split. All patients underwent otoscopy, pure-tone audiometry and speech audiometry in a soundproof room. Frequencies from 250 Hz to 8000 Hz were tested with increasing intensity. Pure-tone average (PTA) was calculated as average of hearing sensitivity at 500, 1000, 2000 and 4000 Hz. All subjects undertook investigation of speech audiometry: speech recognition threshold (SRT; lowest intensity disyllabic words that an individual can repeat at least 50% of the time), PB50 (performance-intensity on phonemically balanced words where 50% of speech is recognized), PBmax (performance-intensity maximum on phonemically balanced words; 100% of speech is recognized). The patients were divided in accordance to classification of moderate or severe hearing loss into 2 groups. Results: We found no statistically significant difference in pure-tone audiometry between aided and unaided ear (P=0.09). In subjects with SHL we found statistically significant difference between aided and unaided ear in SRT (P =0.005), PBmax (P=0.009) and PB50 (P=0.019). In subject with MHL we found no statistically significant difference between aided and unaided ear in SRT (P=0.938), PBmax (=0.644) and PB50 (P=0.612). Conclusion: In our study we show that in subjects with SHL, there is a statistically significant improvement in speech audiometry in the aided ear amongst long term (>5 years) hearing aid users compared to the unaided ear, likely due to increased plasticity of the hearing pathway due to the use of hearing aids. We do not see a similar significant difference in the patients with MHL. Our study has shown that the greater the hearing loss, the greater the benefit of using a hearing aid; this is manifested in the improvement of speech audiometry in long term hearing aid users.