The NEA Working Group on Human and Organisational Factors (WGHOF) is tasked to improve the current understanding of human and organisational performance and the way in which this impacts upon nuclear safety. In order to further the understanding of human and organisational performance during the nuclear plant modification process, the WGHOF organised a workshop in 2003 entitled the “Role of Human and Organisational Factors in Nuclear Plant Modifications”. This technical opinion paper represents the consensus of the NEA member countries which attended.