The Energy Charter Treaty is the first binding multilateral agreement covering the promotion and protection of foreign investment. Energy Charter Treaty applies only to economic activities in the energy sector. This thesis focuses on uniqueness of the Energy Charter Treaty’s investment regime in investor-state disputes. The thesis provides an overview from an international law perspective of such important features of the Energy Charter Treaty as the provisional application of the treaty, the ‘denial of benefits’ clause and the definition of investment. The thesis also analyzes Energy Charter Treaty arbitration cases in order to find whether there exists a consistent practice on crucial jurisdictional questions. An extensive overview was provided regarding Yukos v Russian Federation, Kardassopoulos v. Georgia and Plama v. Bulgaria cases.