The comorbidity of somatic and mental ilnesses is one of the greatest scientific and clinical challenges of modern psychiatry. Patient with mental ilnesses such as schizophrenia and bipolar disorder have an increased mortality rate and shorter life span (10-25 years) compared to general population, not only due to the increased suicididality, but due to increased prevalence of somatic ilnesses such as cardiovascular diseases and type 2 diabetes. Metabolic syndrome, defined as cluster of symptoms like dyslipidemia, hypertension, glucose intolerance and obesity, is most important predictor of earlier onset of cardiovascular disease and premature mortality and it is more prevalent in psychiatric patients than in general population. The main goal of the study was to determine the prevalence of the metabolic disorder and its subcomponents in bipolar disorder patients in comparison to patients with schizophrenia and healthy controls. Furthermore, the secondary goals were to determine the prevalence of increased homocysteine, C-reactive protein and basal cortisol and decrease DHEA serum levels in all three group of participants. We hypothesized that altered levels of aforementioned parameters could be related to the increased risk for development of metabolic syndrome and somatic ilnesses. The study sample consisted of 182 participants divided in the following three groups:59 (32.4%) healthy controls, 60 (33.0%) bipolar disorder patients and 63 (34.6%) patients with schizophrenia. All participants have signed an informed consent document which was approved by local Ethics Committee. All patients were diagnosed according to ICD –X classifications. Biochemical parameters were determined at Biochemical laboratory of University Hospital Center Zagreb. Results of the study showed similar prevalence of metabolic syndrome in bipolar and schizophrenia. Serum homocysteine levels were higher in bipolar group compared to healthy controls, while CRP values were higher in bipolar group than in schizophrenia group and helathy controls. Patients had higher basal cortisol levels than controls. There was no difference in DHEA levels in all three examined groups. Elevated homocysteine and CRP levels are associated with increased risk for the development of metabolic syndrome in patients with bipolar disorder and schizophrenia. Metabolic syndrome, the most important predictor for the development of cardiovascular disease and type II diabetes , is associated with psychiatric disorder per se and it is not exclusively connected with specific psychiatric diagnosis.Our results indicate the possibility for biological typization of bipolar disorder regarding these parameters(homocysteine, CRP, cortisol and DHEA) and evaluation of their influence to the development of metabolic disorder. This could be of , not only theoretical, but practical clinical importance since B-vitamine supplementation could normalize elevated homocysteine levels and thus probably decrease the risk for metabolic syndrome.