BACKGROUND: Recent studies of cochlear implants (CIs) in profound unilateral hearing loss (UHL) patients have demonstrated a restoration of some binaural hearing. AIMS/OBJECTIVES: The objective was to evaluate three possible advantages of binaural hearing in CIs adult users with UHL including single-side deafness (SSD) and asymmetric hearing loss (AHL) subgroups. MATERIAL AND METHODS: A prospective study was conducted that included 70 sequentially implanted patients. Subgroups of these subjects included 64 with a postlingual onset of a profound hearing loss on the implanted side and 6 with a prelingual onset of that loss. Three binaural effects - redundancy, head shadow, and squelch - were evaluated. RESULTS: Significant differences between the 'CI on' and 'CI off' conditions were found for all three binaural effects for the study group as a whole and for the postlingual subgroup. However, results for the subjects in the prelingual subgroup did not demonstrate any of the binaural advantages. CONCLUSION AND SIGNIFICANCE: Patients with a postlingual onset of a profound hearing loss in one ear and normal hearing or only a moderate loss in the other ear are able to make the effective use of a CI in the profound-loss ear in conjunction with acoustic stimulation of the other ear.