As one of the leading causes of death worldwide, suicide is a complex event affected by many factors (such as environment, genetics, and the presence of mental disorder). Differences in genetic background of individuals need to be studied for better understanding of genetics’ part as a risk factor in suicide. The most commonly studied genetic variants are single nucleotide polymorphisms (SNPs). They are single base changes on a specific DNA position, usually with the possibility of being one of two different nucleotides for each position. The majority of researched SNPs in the context of suicide are those in genes of the serotonin signalling pathway, but more recent studies are focusing on genes of other neurotransmitter systems. For example, γ-aminobutyric acid (GABA) as the major inhibitory system with function of maintaining neurochemical balance in a neuronal network. Furthermore, the glutamate signalling pathway showed an important role in synaptic plasticity and excitatory transmission throughout N-methyl-D-aspartate (NMDA) receptors which are in direct contact with polyamine stress response systems. The suicide rate differs between countries all over the world, with Slovenia being among the ones with a very high rate (19.8 suicides per 100 000 citizens according to 2019 data). In this thesis we analysed polymorphisms of genes involved in mentioned systems: in the GABA neurotransmitter system, the gene GABRG2 (rs424740), in the glutamate pathway, the gene GRIN2B (rs2268115 and rs220557), and in the polyamine system, the gene ODC1 (rs1049500 and rs2302614) to determine which alleles are overrepresented in the group of suicide victims in comparison to the control group. After DNA isolation, alleles of each sample were determined with RT-qPCR. As a result of statistical analysis with the PLINK program, all five polymorphisms showed that there are no statistically significant differences in genotype/allele frequency distribution between controls and completed suicide. Only rs220557 showed statistically significant difference in genotype frequency distribution between suicide cases and control, as well as between suicide case done with violent methods and controls, while rs2268115 showed a difference in genotype frequency distribution between suicides done with non-violent methods and controls. Additionally, rs1049500 showed significant difference in genotype frequency distribution between suicide victims that had grave somatic illness and controls. Furthermore, there was no difference in genotype/allele frequency distribution between polymorphisms and suicide subgroups (males, females, violent, non-violent method, addicted, psychiatric patients, and patients with grave somatic illness) in other SNPs. Although the results were negative, they could still contribute to the understanding of molecular genetics in Slovenian suicide victims.