If we try to define a term like mystical experience or to understand the purpose of a cultic practice, we should engage in a very complex investigation. In a short paper like this, there is no possibility of providing a correct and detailed analysis of these questions, only some considerations can be presented concerning the nature and function of Hermetic cultic practices. Therefore, I will analyse a particular phenomenon in detail: the prayer (or as we read in a text, the hymn of praise), which plays a special and central role in the Hermetic mysteries, and what is more, in the cultic practice. In this context I define prayer as one of the main means in the process of communicating with the divine sphere. As it will be seen, the Hermetic prayer has a special structure, which is in connection with its goals. Iamblichus' work about the mysteries provides some important aspects for disclosing this structure, so I will analyze not only the Hermetic but also the Iamblichean text.