The project of the High Speed Railway construction in Baltic States is the largest joint infrastructure project in the post-Soviet era. Rail Baltica (RB) is considered as the most energy-efficient project having the lowest environmental impact.?The aim of the current research is to determine the regional indicators of CO2 emissions intensity of Rail Baltica, based on the project’s energy consumption and carbon intensity of each individual RB Member State.?The approach applied by the author in the current study is based on the significant effects of import/export of electricity by RB Member States and grid losses, in contrast to the local-based method for calculating emissions based on CO2, emission factor of electricity production, recommended by the International Union of Railways. The author's calculations demonstrate the substantial difference in the figures of CO2 emissions intensity between the Lithuanian, Latvian and Estonian sections of the project, which is related to the trainload rate, traffic intensity, CO2 emission factor of Member State. Using RB project as an example, author demonstrates that conclusions regarding the positive environmental effect? of multinational European HSR projects should not be based on average projects ’ indicators, but on the environmental impacts of the project’s sections in each Member State in order to avoid? conflict of interests between the project participants, as well as, the delay in the implementation of such project due to the fact that the asymmetric information received was identified late? by the project’s participants.