Partial deafness is a condition characterised by normal hearing thresholds in low frequencies and increased hearing thresholds (nearly deafness) for high frequencies. Typical hearing aids are rather of a very limited use in this condition as they do not improve understanding of speech. Patients with partial deafness can be presently treated with cochlear implants, which had not been used before due to the risk of damage of hearing remains by electrode introduced into cochlea. The purpose of our study was an objective and subjective assessment of voice quality in partial deafness patients before and after cochlear implantation. The subjects in this study were 25 post-lingual, bilaterally partially deaf patients, 13 females and 12 males. The reference group composed of 55 normal hearing individuals (28 females and 27 males). The acoustic analysis was performed with a multidimensional voice analysis MDVP (Multi Dimension Voice Program), and the subjective assessment was done with GRBAS scale. Initial analysis of voice changes in partial deafness patients was performed versus normal hearing individuals, then voice parameters were measured and perceptual voice assessment was done before and 9 months after cochlear implantation. Measurements of acoustic voice parameters in partially deaf patients showed changes in most of frequency, amplitude, noise and subharmonic components versus normal hearing control group. The most significant, statistically important changes were observed in fundamental frequency variation (vF0), absolute jitter (Jita), jitter percent (Jitt), amplitude perturbation quotient (APQ), smoothed amplitude perturbation quotient (sAPQ), relative average perturbation (RAP), peak amplitude variation (vAm), relative amplitude modulation (Shim), percent shimmer (%Shim), pitch perturbation quotient (PPQ), smoothed pitched perturbation quotient (sPPQ), degree of subharmonics (DSH), degree of voiceless (DUV), number of subharmonic segments (NSH), noise-to-harmonic ratio (NHR), voice turbulence index (VTI). All patients in the study group were subjects to cochlear implantation. After 9 months objective and subjective assessment of patients` voices were performed again. Statistically important changes were identified in average fundamental frequency variability (vF0), relative amplitude modulation index (ShdB), noise-to-harmonic ratio (NHR), number of subharmonics NSH, degree of subharmonics (DSH) and the degree of voiceless (DUV). Comparison of the objective voice parameters changes after cochlear implantation with subjective, perceptual voice quality assessments leads to observation, that improvement of subjective voice quality after cochlear implantation takes place parallelly with improvement of certain objective acoustic voice parameters and some correlations exist. We found, that G correlates with vF0 and Shim, R correlates with DSH and NSH, B correlates with NSH and NHR, A correlates with DUV. We did not prove correlation of S with any of the objective parameters in our research group. Our study proved, that acoustic and perceptual features of voice in partially deaf adults are different than in normally hearing people and cochlear implantation in partial deafness patients is an effective tool to improve hearing and leads to improvement of the acoustic structure of the voice.Partial deafness is a condition characterised by normal hearing thresholds in low frequencies and increased hearing thresholds (nearly deafness) for high frequencies. Typical hearing aids are rather of a very limited use in this condition as they do not improve understanding of speech. Patients with partial deafness can be presently treated with cochlear implants, which had not been used before due to the risk of damage of hearing remains by electrode introduced into cochlea. The purpose of our study was an objective and subjective assessment of voice quality in partial deafness patients before and after cochlear implantation. The subjects in this study were 25 post-lingual, bilaterally partially deaf patients, 13 females and 12 males. The reference group composed of 55 normal hearing individuals (28 females and 27 males). The acoustic analysis was performed with a multidimensional voice analysis MDVP (Multi Dimension Voice Program), and the subjective assessment was done with GRBAS scale. Initial analysis of voice changes in partial deafness patients was performed versus normal hearing individuals, then voice parameters were measured and perceptual voice assessment was done before and 9 months after cochlear implantation. Measurements of acoustic voice parameters in partially deaf patients showed changes in most of frequency, amplitude, noise and subharmonic components versus normal hearing control group. The most significant, statistically important changes were observed in fundamental frequency variation (vF0), absolute jitter (Jita), jitter percent (Jitt), amplitude perturbation quotient (APQ), smoothed amplitude perturbation quotient (sAPQ), relative average perturbation (RAP), peak amplitude variation (vAm), relative amplitude modulation (Shim), percent shimmer (%Shim), pitch perturbation quotient (PPQ), smoothed pitched perturbation quotient (sPPQ), degree of subharmonics (DSH), degree of voiceless (DUV), number of subharmonic segments (NSH), noise-to-harmonic ratio (NHR), voice turbulence index (VTI). All patients in the study group were subjects to cochlear implantation. After 9 months objective and subjective assessment of patients` voices were performed again. Statistically important changes were identified in average fundamental frequency variability (vF0), relative amplitude modulation index (ShdB), noise-to-harmonic ratio (NHR), number of subharmonics NSH, degree of subharmonics (DSH) and the degree of voiceless (DUV). Comparison of the objective voice parameters changes after cochlear implantation with subjective, perceptual voice quality assessments leads to observation, that improvement of subjective voice quality after cochlear implantation takes place parallelly with improvement of certain objective acoustic voice parameters and some correlations exist. We found, that G correlates with vF0 and Shim, R correlates with DSH and NSH, B correlates with NSH and NHR, A correlates with DUV. We did not prove correlation of S with any of the objective parameters in our research group. Our study proved, that acoustic and perceptual features of voice in partially deaf adults are different than in normally hearing people and cochlear implantation in partial deafness patients is an effective tool to improve hearing and leads to improvement of the acoustic structure of the voice.