Nowadays, due to the continuous development of psychological sciences, we observe an increase of the interest in imagination, and undoubtedly the role of imagination in mental simulations. When exploring the issues of the subject matter, it is necessary to note that the ideas of imagination and ideas were for a long time neglected in research and analyzes. To a certain extent, this is reflected in the literature on the subject of this research topic; however, in my opinion, in both Polish and foreign literature, there aren’t sufficient scientific studies devoted to this issue and its potential impact on the life of every human being. The principal aim of this work is to analyze the idea of imaginations presented in Petrażycki’s theory – their nature, functions and types – and to discuss mental simulations and examples of their use. In addition, another relevant issue is going to be analysed – the connection and the relationship between imaginations in the past and mental simulations in present time. The article will present how to leverage these ideas.