In this article we analyse the provisions of the European Union (EU) Lishon (Reform) Treaty and try to predict their future impacts on EU environmental governance. The Treaty could, if and when ratified, introduce changes to the EU's general principles and objectives, competences, institutions and policy procedures that may have a significant bearing on future patterns of environmental law and policy-making in the EU. But previous experience suggests that Treaty amendments tend to be "obligationally incomplete". that is subject to extensive post-treaty interpretation and contestation. Consequently, it may take many years for the full impacts of the new Treaty to reveal themselves should ratification ever be completed.