Based on the project assignment in the course "Construction Organization II", entitled "Planning of Cash Flow in Building Construction Projects", a cash flow plan was created for the construction of the University Library and Multimedia Centre building in Osijek. Some of the problems that construction companies nowadays face in Croatia are presented, as well as the importance of the Project of Construction Organization for the successful implementation of construction projects. Detailed planning in general is explained in addition to all the elements needed to draft the plan. Moreover, all the goals that to be achieved by plan development are listed. The importance of quality planning for each individual construction project is emphasized. There is also a detailed demonstration of the procedure in which a complex building structure is broken down into smaller parts that are measurable and therefore calculated separately to then be linked to the preparation of the initial plan according to the principle of analysis and synthesis. WBS and OBS have been thoroughly analysed and constructed for the given construction, both separately and in a combination. The latter, in the selection of activities, links parts of the project's content to the management roles and responsibilities and the execution means, i.e. their executives. Such a combination is the basis of all project planning documentation and project execution control. Through defining of the required work for activity completion, determining the time needed for their implementation and linking activities to each other, a dynamic plan has been created, based on the chosen planning method. After drafting the initial plan, monitoring and control of project implementation are being conducted, with an important focus on plan optimization. A graphical representation of the cumulative costs in time, i.e. S-curve is illustrated and explained. Through the monitoring of the project, changes were made in the timeline and the cash flow plan and the impact of the change on the S-curve was observed.