Purpose: The main objective of this research is to identify the impact of parallel performance of various tasks on the individual effectiveness. Moreover, a methodological goal was set for the research to explore the possibilities of using eye-tracking in the studies of multitasking. Design/Methodology/Approach: The study was conducted in the form of an experiment. All participants worked at the same computer station time was measured with Eye Tracker. Findings: It was confirmed that multitasking requires more time to accomplish tasks and deteriorates creativity, but not correctness of the answers in case of simple tasks. Interestingly, in case of multitasking under time pressure, the performance was worse. Practical Implications: Deeper understanding of the determinants and effects of multitasking on organizational and individual performance enables the adjustment of work organization and management style in order to achieve optimal results. Originality/Value: This paper brings new insights to the studies of multitasking not only in terms of the results of an experimental research, but also in terms of methodological concerns like eye-tracking as a new method of empirical diagnosis.