The paper examines the performance of the UN Economic Commission for Europe (UNECE) in the field of transport, environment and health. In the course of the study, the tasks of reviewing and summarizing the main arguments of supporters and critics of UN activities in this field and forecasting the development of its potential in the future, the institutional features of the reforms to achieve sustainable development, as well as the most important problems of the green economy are performed. The authors emphasize that in the recent 25 years environment protection has become a priority for the UN activity. Additionally, international conferences on environmental issues and sustainable development have been an important tool to define global priorities, to raise awareness about these issues and to draw attention to essential problems that can be neglected. According to the authors of this study, no matter how inspiring the tendency of the growth of the number of specialized agencies involved in solving problems of transport, environment and health, these efforts are clearly not enough. The paper substantiates the conclusion that today the UN is the only global organization with the required resources to be able to positively influence the sphere of environmental protection. At the same time, comprehensive institutional mechanisms to improve the transport system, environmental protection and the coordination of health strategy are needed within the framework of the activities of the specialized UN agencies.