The project as a temporary organizational structure created with the aim of realizing the project delivery within the given time frame, has no organization or resources at the beginning. All this is formed after project goals are determined. In this thesis the organizational structures of the participants according to the contract model, manner of work and the professional association called FIDIC were elaborated. Contractual models are outlined, each of which defines the position of project participants, and has an impact on their relationship and organization. The method of assessing this impact is the risk exposure measure in relation to the flexibility and initiative of participants, whose presentation is explained in this thesis. Each contractual relationship is defined by an organizational scheme. The graphic representation of a project, WBS, is the foundation for project management, communication and decision-making, and the ultimate goal of its creation is to connect with the OBS (structural breakdown of the organization). Integrated structures provide a project management model on which all project planning documents and project execution plans are based. Construction contracts as a very frequent contract type, due to their complex and challenging nature, have provided special regulation - the general conditions called FIDIC. The aim of the general terms is to define contractual guidelines among the participants who serve the regulation and legal arrangement of the relationship. Although FIDIC conditions are not perceived as ordinary contractual terms, Croatian law in contractual relationship with FIDIC is preferable to the application of the Civil Obligations Act. Practical part of the thesis contains schemes with examples of contractual relationships from practice. Four examples of high-rise and low-rise buildings are presented with a traditional organizational structure.