Aim: The study objective was to evaluate the effect of unilateral cochlear implantation with direct stimulation of the VIIIth cranial nerve in adult patients, with profound perceptive hearing loss, with an emphasis on parameters of pure tone audiometry and speech intelligibility using speech audiometry. Materials and methods: A retrospective analysis of patients with unilateral cochlear implantation at the Department of Otorhinolaryngology and Head and Neck Surgery during the period 1/2012-12/2017. The number of patients n = 68, men = 29 (43%), and mean age 44 (18-87) years. Results: Pure tone audiometry - preoperative mean pure tone average (PTA) 101.1 +/- 10.8 dB HL, postoperative mean PTA 40.1 +/- 8.4 dB HL, mean PTA difference before and after surgery 60.9 +/- 14.4 dB HL (p < 0.01). Speech audiometry (SA) - preoperative mean value of maximum speech intelligibility 8.4 +/- 14.4%; postoperative mean SA 56.5 +/- 19.4%, mean SA improvement before and after surgery 48.1 +/- 22.1%; (p < 0.01). Postoperative Nottingham scale - 15 (22.1%) patients achieved grade 7, 25 (36.8%) patients achieved grade 6, 16 (23.5%) patients achieved grade 5, 9 (13.2%) patients achieved grade 4, 2 (2.9%) patients achieved grade 3, and 1 (1.5%) patient achieved grade 2. The age factor did not reveal any significant difference for functional outcome of surgery (the patient groups <= 50 years, 51-65 years, > 65 years) - no significant differences in PTA and speech intelligibility for SA among all age groups (p > 0.05) was observed. Conclusion: In post-lingual deaf patients who no longer benefit from hearing aid fitting, the cochlear implantation with direct stimulation of the auditory nerve is a highly effective method of correcting hearing function. A signifi cant improvement in speech discrimination and verbal communication without latency, representing a substantial benefit for the quality of life of implanted patients, is achieved by unilateral cochlear implantation. Concurrently, no evidence of dependence was found between age at the time of surgery and postoperative outcome.