In each and every cell of our body there is the same genetic code. What is it then that makes one cell a brain cell and another one a muscle cell? Which cell will become a part of the skeletal system and which one will be a part of the digestive system? Epigenetics offers the answers. Epigenetics is an exciting part of science that studies the epigenome. It studies the mechanisms of gene activation and gene suppression without changing the DNA molecule itself. DNA methylation, histone modification and system of interfering RNA molecules are cellular mechanisms of epigenetic regulation. However, malignant cells have a dysfunctional regulatory epigenetic system and that is the reason why they are out of control. New drugs that aim to use these regulatory mechanisms and in that way bring the „unrestrained“ malignant cells under the control of the organism have emerged recently. Therefore, treating and curing the malignant disease from different perspective is achieved. Aim of this thesis is to provide an overview of epigenetic drugs available nowadays as well as to describe mechanisms of their action and targets of their application. Drugs described in this thesis were selected based on their US Food and Drug Administration approval.