This is a publication that aims to present in a synthetic and easily understandable way the existing knowledge about the potential environmental impacts of marine renewable energy projects and to point to the methodological means for studying them, so that future projects of this nature can be sustainably managed from an environmental perspective. In this respect, it will be useful to the promoters of marine renewable energy projects so that they take in to account all the environmental implications of their projects. It will also benefit the technicians of the administrations involved in Environmental Impact Assessment (EIA) of projects and in the granting of the relevant permits, as well as the people who carry out EIS. Finally, it will be of interest for other groups like NGOs, which are devoted to preserving, conserving and protecting the marine environment, and also for the public in general. This initiative is part of the project on the efficient and integral use of renewable offshore energies “CENIT-E OCEAN LEADER, leaders in Ocean Renewables”. The project is an ambitious technology initiative promoted by a consortium of companies with a strong research capability which addresses the challenge of developing the necessary technologies to set up integrated installations that can harness marine renewable energies, such as waves and tidal currents. Further information can be obtained at www.oceanlider.com. The main aim of the OCEAN LIDER project is the research in breakthrough technologies needed for the setting up of integrated facilities for the use of renewable ocean energy, thus contributing towards: the sustainable use of marine energy resource; the development of new products, processes and services of strategic importance to the sectors involved; to promote a new economic growth model based on renewable energies and energy saving; to contribute, with renewable resources, to energy supply, addressing the Spanish and European priorities (20%, 2020) and offsetting the trade balance; obtaining energy sustainability and combating climate change (reduction of GHG emissions); enabling Spain to remain the global renewable energy leader, helping generate skilled employment and combating climate change and gain access to Greenhouse Gas allowances. One of its six lines of research is devoted to the development of models, protocols, guides, methodologies, tools and new technologies in order to asses correctly the environmental impacts on the full cycle of offshore energy-generating infrastructure projects.