The purpose of this paper is to review the lessons learnt on the use of advanced materials on the design and operation of components in fission reactors and to consider how these lessons can be employed to benefit the use of advanced structural and, to a certain extent, coolant channel materials in the design and qualification of the in-vessel and containment vessel components for the DEMO fusion reactor. The focus is on lessons learnt on methodologies that need to be applied, and a number of specific recommendations are made.