It is important for a contractor to know which points should be emphasized when negotiating a project, and what factors need to be considered in order to ensure that the project will be as successful as possible. This research focuses on effective project management within construction projects, and the factors that affect project success. This was done by looking at two similar projects executed at the same time with two different project managers. One client was a non-profit organization run without profit goals, and the other client was a real estate development company with investment in mind. The works started in a different way, as one project took part in the design phase from the beginning and had a fixed unit price, while the other consisted only of the execution of the project and a cost-plus contract. The results of the projects turned out to be different in terms of schedules and profits. One client has continued to use the relevant contractor for many other projects, while the other client did not want to continue working with the contractor. Qualitative methodology was used during the research and enabled the researcher to gain deeper insight into the experience of the project managers in their work. Information was also obtained about the tools that the project managers used to secure the project\'s finances, schedules, quality, and other important issues. Two interviews were conducted with senior project managers in the team. The answers given by the project managers were then compared and analysed to determine what caused their projects to produce the results they did. The main findings involved the importance of positive communication and trust, especially between contractors and the client, but also within the overall project, within the team, subcontractors, suppliers, and designers. Another factor that greatly affected the success of the projects was organisation, including the recording of data, whether it was about schedules and the processes followed to meet a specific schedule; or financial management, including keeping track of additional work and deviations, as these items are often costly and come up in the end of the project when the settlement begins on unresolved items. At the same time, keeping track of the quality of the project is also important, as is, again, recording reviews, deviations, and mistakes, as they can be both costly and time-consuming.