OBJECTIVES: Cochlear implantation is rapidly gaining acceptance as the most effective treatment for adult patients with unilateral deafness. The benefits for the pediatric population remain to be investigated. This study aimed to investigate the implications of cochlear implantation in children with congenital and noncongenital unilateral deafness. DESIGN: Four children, three with congenital and one with a sudden unilateral deafness, were studied after implantation. The children were aged 17 months, 4.5 years, 6.8 years, and 9 years at the time of implantation. Speech perception in noise and sound localization ability were evaluated using age-appropriate materials. RESULTS: The child with postlingual unilateral deafness rapidly integrated the normal acoustic hearing with the electrical signal from the cochlear implant and showed binaural benefits, as indicated by the localization ability and the improvement of speech perception in noise scores. The younger child with congenital unilateral deafness showed some clinical evidence of binaural integration and the two older children with congenital deafness have not yet indicated signs of binaural benefits. CONCLUSION: It seems that cochlear implantation in children with congenital unilateral deafness may provide some of the benefits of binaural hearing if implantation occurs within the critical period for bilateral auditory development.