The paper describes development of a continuous and discrete model of human resources transitions in a large organization. The model considers eight different ranks. The calibration of the model was performed where the historical data was used to determine time constants of transitions and fluctuations. Several simulation runs were performed in order to complete predictive validation of the model. Optimization of the model was performed in order to achieve desired structural dynamics. Pattern search algorithm was applied at this stage while considering the key parameters’ limitations. By performing the optimization appropriate strategy of the system structural development could be determined. Development and comparison of the continuous and discrete event model was performed. The discrete event model was applied in the validation phase. The hybrid approach to the problem provided higher level of confidence. System dynamics methodology proved to be appropriate as the tool for initial development of the model and structural validation reference.