The given paper focuses on the opportunities how to use eye-tracking systems in the field of cognitive science and HCI. We have shown both possibilities of a table based eye-tracking system (SMI RED 250) for the laboratory studies and a head mounted system SMI HED50. The aim of the paper is to define the basic task for an eye-tracking technique to solve. We have achieved such tasks as cognitive studies, the studies of GUI, HCI and the psychology of programming. The obtained results have been provided for each task.