Energy security is one of the special spheres of national security. The lack of strategic resources may be an obstacle for any country to prosper. With insufficient raw materials, national industries are devoid of energy in large quantities, so that it has a huge negative impact on economic growth. For the reason to prevent such a situation, many states are induced to establish a separate field of external interests and actions - energy diplomacy. In terms of energy diplomacy we consider nuclear potential as a specific issue. This concept includes both military and peaceful aspects, from weapon of mass destruction to nuclear power plants. On the one hand, the number of states which legally possess this weapon is limited. In this sense, nuclear potential provides with particular status in international affairs as well as global responsibility. On the other hand, different countries seek for diversification of energy supplies (or to base their energy sector primarily on nuclear power). Therefore, nuclear potential has a significant importance in economic terms. In this article we examine cases of the use of nuclear potential in energy diplomacy of two selected countries - France and Sweden. The French nuclear system is a typical case of double nature of nuclear technologies. The country has both military and peaceful capabilities. They were established in 1960s by the will of the president Charles de Gaulle who advocated the idea of national sovereignty. With the enlargement of nuclear system, nuclear power plants still generate more than 70% of energy in national scale. The public opinion is currently divided on how to balance advantages and disadvantages of nuclear technologies. Sweden maintains the use of one-track nuclear capability. After the Second World War it was close to launch its own nuclear program. In 1950-1960s the government tried to impose social consensus on the point. However, high prices of the projects as well as the opposition criticism lead the country to the orientation toward peaceful technologies. Swedish government has recently begun to abandon them too by ratification of legal acts restricting the construction of new nuclear plants.