Current pharmacotherapy for psychiatric disorders is partially effective. Many patients do not respond well to therapy and suffer from adverse effects, which results in poor patient compliance and poor treatment outcomes. Because of the need to understand the differences between individuals in response to drug pharmacogenomics has developed, a science that studies the role of the genome in response to a drug. This review paper aims to address the achievements of pharmacogenomics in understanding which genetic factors, and how, affect the therapeutic efficacy of psychopharmaceuticals. Pharmacogenomics is explained in more detail in the introduction. Then, at the beginning of the elaboration of the paper, some of the main receptors, ie enzymes whose different phenotypes are associated with a different response to the psychopharmaceutical, were mentioned. As the knowledge of pharmacogenomics expands, so does the list of actors who also participate in the patient's unexpected response to the drug, and they are mentioned throughout the text. Furthermore, the paper deals with four main groups of psychopharmaceuticals (antidepressants, antipsychotics, mood stabilizers, and anxiolytics & sedatives & hypnotics), ie their representatives who were selected because of their importance, but also because they accurately depict how genetic polymorphisms can affect them. Finally, the paper discusses two important topics of pharmacogenomics. Challenges, socio-economic and ethical, of pharmacogenomics and the difficulty of introducing genetic tests into everyday clinical practice, but also of a promising future that could bring personalized, patient-tailored medicine.