Proteomics is a branch of biological sciences concerned with proteome research. Proteome studying involves structural and interaction analysis of proteins on a large scale, especially their position and function. As protein expression is the mediator of genetic vulnerability, proteomics is enabling research into etiology of psychiatric disorders through discovery of potential biomarkers. They can be found by comparing qualitative and quantitative protein expression data from healthy and diseased individuals using the technique of differential display. Biomarkers could fill the gaps in the extremely complex diagnostics of posttraumatic stress disorder (PTSD), and potentially show the direction for further development of pharmacotherapy. Previous studies have shown qualitative and quantitative changes in the brain, cerebrospinal fluid and peripheral tissue proteins in many neurodegenerative and some psychiatric disorders. In this pilot study our aim was to show differential display of the proteomic profiles from the serum of three patients with combat-related PTSD as compared to three healthy controls. Chosen participants with PTSD were of similar age, had similar traumatic experiences and were on similar medications, with no psychiatric comorbidities. Large-scale proteomic approach and mass spectrometry with the use of human proteomic databases were employed as identification tool for discovering the differences between serum proteomic profile in PTSD and healthy controls. In this pilot study we found 122 qualitatively different proteins and more than 22 quantitative differences between individuals with PTSD and healthy controls. These results indicated direction for a larger analysis of this type in people with PTSD. Selected group of proteins found in differential display of the 2D gels will be used for identification of biomarkers in further studies. This pilot study offers a good basis for further proteomic research, which could help in better diagnosis and treatment of PTSD, as well as clarification of its etiology.