Greece is a country with a relatively high energy potential. Especially its renewable energy potential is worth mentioning as the strong winds and the sunshine days are a characteristic of the region. Its oil and natural gas reserves may also be remarkable. Greece is also a country facing a strong financial crisis. High rates of unemployment, uncertainty in the economic sector and lack of investments are some of the problems Greece has to deal with. In order to deal with the crisis and regain its credibility Greece needs to boost its economy and the best way to do it is through investments. Taking into consideration the fact that the energy sector in Greece can be further developed and invested, the investments in this sector are considered necessary. On the other side, energy is a sensitive issue for the state. It is connected with national safety and security and that is the reason why it is in a high degree regulated from the state. In other words, the state needs to be able to control the energy sector and to intervene when necessary. Energy is also connected with public interest. Taking into consideration the fact that energy investments often cause negative effects to the natural environment and to human health, the intervention of the state becomes even more important. This thesis refers mainly to the connection of the energy investments with the protection of the environment. The protection of the environment is an obligation for the state and belongs to public welfare interests. As such, the state has the right and at the same time is obliged to take preventive measures for its protection and to intervene in case this good is in danger. But at the same time and especially during an economic crisis the state also legislates for the boost of investments. These laws are often violating the need for environmental protection. In the first part of this thesis the main laws regarding environmental protection and energy investments are examined and the most famous jurisdiction of the Greek Administrative Supreme Court regarding energy investments and the protection of the environment are presented. In the second part of this thesis ways for the protection of foreign investments are explained. A detailed presentation of protective clauses in international and bilateral investment treaties follows. The link between clauses, such as fair and equitable treatment and indirect expropriation with the protection of the environment are explained and relative tribunal decisions are presented. The aim of this thesis is to show that a conflict between energy investments and the protection of the environment is inevitable. But both energy investments and a clean environment are essential for humans and must coexist. The key is that investors respect the surrounding environment and through corporate social responsibility take measures for its protection. On the other side the state must regulate energy and environment sector and avoid a very strict environmentally friendly policy that exclude investors.