Healthcare policy-makers have struggled to decide whether deaf children should receive unilateral or bilateral cochlear implants. Decision-making has been hampered by a paucity of data on the additional quality of life associated with bilateral implantation. Such data are needed to inform judgments of cost-effectiveness. We report estimates of the additional quality of life which we combined with estimates of the additional costs of providing and maintaining two implants rather than one. The results show that, on the balance of probabilities, bilateral implantation is a cost-effective use of healthcare resources in the United Kingdom. Our methods for eliciting judgments of quality of life, and for relating costs and benefits to decision criteria, are relevant to all healthcare systems.