Cochlear Implants enhance communication, but they do not fully replicate natural hearing, making ongoing audiological support essential for optimal outcomes. Cochlear implants have played a pivotal role in improving the quality of life of children with pre-lingual hearing loss and adults with post-lingual hearing loss to re-enter the hearing and social world. Similarly, children with severe to profound hearing loss can now be integrated into mainstream education due to hearing restoration by cochlear implants. Therefore, the selection of suitable candidates is most important for the success of advanced technology like cochlear implants in this era. This chapter discusses the assessment of audiological candidacy for cochlear implantation from the findings of an extensive series of evaluations for children and adults.