Although there are numerous papers on the topic of personality disorders and eating disorders, the current essential understanding of these disorders is still insufficient, which can be seen primarily in the modest success of the treatment of these disorders. This review paper presents what is considered to be the most important parts of the psychodynamics of personality disorders and eating disorders to further illuminate possible pathways leading to good treatment outcomes for these disorders. Psychodynamic theory of development encompasses theories that were originally developed based on Sigmund Freud’s work and his psychoanalysis. Our inner life and all our personal experiences, feelings, desires, and fantasies govern us and directly affect our behavior and communication with the environment. I defined the psychodynamics of personality disorders through the strength of the individual's ego, defense mechanisms, and object relations and representations. Additionally, understanding introjects can help spot differences about how patients see themselves and the people around them. The focus of my work on the psychodynamics of eating disorders is attachment theory and reflective functioning, but also the way in which emotional experience affects the individual and the development of eating disorders. In addition to psychodynamics, this review paper also deals with the epigenetics of these disorders, which helps to understand their etiology. Epigenetics is a scientific discipline within genetics that studies inherited changes in gene expression that are not caused by change in the DNA sequence. An overview of epigenetic modifications tells us about the important interaction of genes and the environment throughout an individual’s life. How the environment affects gene expression is of great importance in understanding the causes of disorders whose understanding can contribute to preventing the onset of these diseases.