This paper proposes a definition process of the project structure which should be constructed in order to reach the objectives and to deliver the final results. The first part of the paper specifically describes this process, with its inputs, tools and methods and outputs. The inputs of this process, initial situation, objectives and environment, are described in part 2, with research proposals on environment management. Other research proposals about tools and methods are presented in part 3, focused on the topics of scope and activity definition and resource assignment. Concrete propositions stemming from research works and from their application at VALLOUREC and PSA PEUGEOT CITROEN will be presented all along the paper.