63 years old patient with progressive bilateral mixed hearing loss since 15 years there was a suspicion of cochlear otosclerosis. He used hearing aids but complained of huge discomfort of hearing. The decision was made to surgically treat this hearing loss using middle ear implant MET by Cochlear company. The surgery from posterioauricular approach confirmed restricted mobility of ossicular chain. There was a necessity of placing implant in round window to stimulate through round window membrane. The other part of implant was fixed in antomastoidectomy and in the cortical part of temporal bone.