Contemporary psychiatry pays more and more attention to the patient's capacity regarding acceptance of psychiatric drugs. Understanding the basis of our treatment's effectiveness becomes more challenging. To understand psychiatric treatment psychiatrists must pay full attention to mentalizing and the conditions under which this basic human capacity becomes impaired especially in those suffering from personality and eating disorders. This paper discusses the meaning and clinical applications of the mentalizing related to psychopharmacotherapy for personality and eating disorders patients, including suicidality.