Abstract The present article describes the arbitral proceedings in the investment dispute between Italy and Cuba, with special regard for the Final Award rendered in 2008. The arbitration has raised a number of interesting issues in the application of customary international law, including the admissibility of claims in diplomatic protection in investment disputes under a BIT, the application of the rule on the exhaustion of local remedies, the attribution of acts of State-owned enterprises to the State and the use of general international law as a means to interpret treaty provisions defining the scope of the BIT. Some of these aspects have proved particularly controversial, as shown by the thorough dissenting opinion attached by arbitrator Tanzi, and they are critically analysed. The arbitration confirms the profound interdependence of bilateral treaties and customary international law in international investment arbitration.