Because of high resource prices for rare earth elements over the last decade, companies and governments are investing in research in finding new deposits and innovations. The purpose of this thesis is to measure the potential of rare earth deposits in the deep-sea environment. This is done by a wide and extensive literature study with a focus on supply and demand, combined with several cash flow analyses. Some research will be on alternatives for deep-sea mining; for example recycling and substitution of rare earth elements. Obstacles like the public opinion and the United Nations Convention on the Law of the Sea, which can square up the potential, will be discussed as well. This thesis shows that conventional mining methods can answer to the world demand for the next 40 years. Nations with high demand, but without resources, can also be supplied for the upcoming 30 years. On top of this, cash flow analyses show that mining of rare earth deposits in the deep-sea environment will not be economically feasible in the foreseeable future. Also, the ecology of the deep-sea is unique and is already starting a public debate. Furthermore, it is almost impossible to start mining in international waters, as the United Nations Convention of the Law on the Sea prohibits this. Although recycling and substitution developments are in their infancy, nations and mining companies invest in these alternative methods. It is more likely for nations to continue to invest in these technologies rather than deep-sea mining. All-in-all it can be concluded that the potential of rare earth deposits in the deep-sea environment will be extremely low during the upcoming decades.