The focus of this paper is the ecology of oil and gas infrastructure and the potential ecological impacts from decommissioning in place and reefing. Many offshore oil and gas structures are approaching the end of their operating life, yet our understanding of the environmental effects of different decommissioning strategies is incomplete. Leaving certain components of offshore structures in place can have positive impacts on the environment. This needs to be demonstrated on a case by case basis through a robust environmental assessment which is critical to stakeholder support.