Our objective was to compare outcomes in speech and quality of life in those undergoing cochlear implantation for single-sided deafness (SSD), with the aim to characterize the clinical impact of underlying diagnosis in the affected ear and pre-operative hearing status.Prospective case series.Academic Cochlear Implant Center.42 adult patients implanted with the diagnosis of SSD.Patients were evaluated at 3-, 6-, and 12-months post-operatively using AZBio sentence and speech, and consonant-nucleus-consonant (CNC) depending on appropriate testing level. Our previously validated Comprehensive Cochlear Implant Quality of Life (CCIQ) questionnaire was administered.Speech perception, quality of life.Subjects were stratified by the underlying diagnosis: Meniere's Disease (MD; n = 10), sudden sensorineural hearing loss (SSNHL; n = 13), and Other (eg TBI, acoustic neuroma, progressive, noise-induced; n = 19). Mean preoperative PTA of the implanted ear was 82dB ± 17; that of the nonimplanted ear was 32dB ± 17. SSNHL and MD demonstrated the highest speech perception score at 3 months (93 and 95%), and "Other" demonstrated the lowest scores at 88%. All 3 groups demonstrated nadir in speech scores at 6 months before improving at 12 months, but the "Other" diagnoses maintained the lowest speech testing across all time points. All 3 groups reported improved quality of life on CCIQ.Subjects with SSNHL and MD demonstrate excellent speech perception and quality of life outcomes after cochlear implantation for SSD. Subjects with "Other" diagnoses underlying their SSD demonstrated lower scores on speech testing but nonetheless reported improved quality of life.