While refurbishments for the long-term operation of nuclear power plants and for the lifetime extension of such plants have been widely pursued in recent years, the number of plants to be decommissioned is nonetheless expected to increase in future, particularly in the United States and Europe. It is thus important to understand the costs of decommissioning so as to develop coherent and cost-effective strategies, realistic cost estimates based on decommissioning plans from the outset of operations and mechanisms to ensure that future decommissioning expenses can be adequately covered. This study presents the results of an NEA review of the costs of decommissioning nuclear power plants and of overall funding practices adopted across NEA member countries. The study is based on the results of this NEA questionnaire, on actual decommissioning costs or estimates, and on plans for the establishment and management of decommissioning funds. Case studies are included to provide insight into decommissioning practices in a number of countries.