The topic of this article is the management of projects in contests with a high level of uncertainty for echnological or market reasons or for the behaviours and the decisions of the actors that interact with the project. This uncertainty influences the gaining of project’s objectives and makes very difficult its management and is not completely faced with traditional instruments and methods of the organizational and managerial model of Project Management. The causes and the effects of this kind of uncertainty are analysed with particular attention to the decisional processes, to the collocation of the decision maker in the project and to the result of decision process obtaining, in this manner, a classification of projects. To every class of project so obtained, methods for improving the control of the project are associated with a consequent growth of the probability of gaining the defined project’s objectives. The opportunity for this job is furnished by three cases, described in the introduction, that are examples of similar situations. The cases are here analysed to define the impacts on some relevant aspects of Project Management: the set of objectives, the way for the measure of obtained results, the methods and the techniques for controlling the project and the technique of risk management. The analysis will show that the projects considered in this article, for an effective management, need of an improved organizational and managerial model of Project Management.