This MSc dissertation focus is on the relationship of poetry and psychoanalysis, seeking to understand the importance of the first for the theoretical construction of the second. Thus, initially a brief tour on poetry is made, and then we enter the work of Freud questioning why he quoted the poets so often. Accordingly, the distinction between primary and secondary processes, in addition to the concepts of facilitation (Bahnung) and deffered action (Nachträglichkeit) are investigated as important concepts to approach poetry originality. In a second moment of dissertation, from the Derrida`s notion of difference, the use of poetry as an illustrative example of the effectiveness of a theory is questioned. This discussion takes as its starting point the seminar of Lacan on The Purloined Letter of E. A. Poe and its conclusion that a letter always reaches its destination.