Vestibular lesions are found after cochlear implantation in 23-100 % of cases. The objectives of this study were to evaluate the vestibular function before and after implantation while focusing its feasibility. This prospective study included 35 patients, mean age 49 years. Each patient enjoyed a vestibular balance before and after implantation in a median period of 5 months compared to surgery. Vestibular evaluations were performed using vestibular-evoked myogenic potentials (VEMP) and videonystagmography. Before implantation, the VEMPs were bilateral in 73 % of cases. They are modified after implantation for 13 patients, including 12 missing or reduced potentials on implanted side (p = 0.0015). Caloric tests found themselves a significant decrease in the reflectivity of the ear implanted (p < 0.0001). Vestibular symptoms were independent of changes on vestibular tests. No relation was found between the occurrence of post-operative vestibular symptoms and the results of the vestibular investigations. However, the achievement of these exams is not easy especially for children and only part of the vestibule is tested. In conclusion, the vestibular assessments help to choose the side of implantation, assess the pre-operative vestibular condition and assess and locate vestibular lesions induced. Further tests should enable a complete vestibular assessment.