Mortality rate from chronic non-infectious diseases (coronary heart diseases, diabetes mellitus, and chronic liver disease) in Lithuania is far higher as compared to the European Union average. In 2007, Lithuania ranked third among EU member states according to mortality rate indicator for cardiovascular diseases of males aged 20–64. The most frequent manifestation of cardiovascular diseases is the coronary heart disease (CHD). Epidemiological studies revealed the most important risk factors of chronic non-infectious diseases. Moreover, new elements in the pathogenesis of atherosclerosis have been identified, i.e. oxidized low-density lipoproteins, antioxidant vitamins and fatty acids. Fatty acids (FA) are oxidation markers, since they participate in lipid peroxidation as substrates. The most sensitive to peroxidation are the polyunsaturated fatty acids (PUFA). On the contrary, essential PUFA are important for synthesis of eicosanoids. When too little or too much of fatty acids are consumed with food, certain health disorders arise. A common cause of FA imbalance is too abundant consumption of animal fats and insufficient consumption of vegetable fats. This may cause chronic non-infectious diseases. The FA of human body influences the metabolism of other substances, therefore, the study of such metabolic correlations comes of relevance in exploring the pathogenesis pathways of diabetes mellitus, liver and kidney diseases. The purpose of the present review is to evaluate fatty acids as biomarkers as well as their implications for the etiopatogenesis of chronic non- infectious diseases. Our research has shown that a higher quantity of polyunsaturated fatty acids in the group of Lithuanian males aged 50 and lower blood levels of antioxidants reflect insufficient protection of lipids from oxidation and, obviously, this may be one of the risk factors predetermining accelerated atherosclerosis and a higher morbidity of cardiovascular diseases. The main factors that influence LDL susceptibility to oxidation are long-chain polyunsaturated fatty acids, α-tocopherol and the plasma concentration of triacylglycerols. Lower γ-tocopherol concentration in the group of Lithuanian males may imply that the Lithuanians take less of the vitamin with food, while oxidation processes proceed more rapidly. It is likely that higher plasma concentration of 7ß-hydroxycholesterol in the Lithuanian men is determined by the more intense lipid peroxidation in vivo. Our research has shown that patients with CHD have considerably lower blood levels of PUFA. This may impact on the synthesis of antiatherogenic eicosanoids and thus may be an atherogenic factor. The general quantity of polyunsaturated fatty acids in the adipose tissue in individuals with glucose tolerance disorders, also patients with diabetes mellitus is lower, its level possibly being related to the degree of metabolic disorder, more rapid mobilisation of fatty acids from the adipose tissue or to smaller quantities of essential PUFA (linoleic acid and α-linolenic acid) consumed with food. The data allow us to assume that PUFA enriched food may cause an increase of the blood levels of adiponectin, an important antiatherogenic and anti-inflammatory factor. The positive relationship between n3 PUFA and leptin concentrations suggests that abundant consumption of PUFA may determine an increase of leptin levels in blood. PUFA do not influence the resistin metabolism in human body, however, some saturated and monounsaturated FA may relate to resistin concentrations in blood. Individuals with chronic liver disease take sufficient quantities of essential polyunsaturated fatty acids and their resorption is not upset. Also, the chronic liver disease patients show no signs of increased deterioration of reserve lipid tissue. Fish oil (source of n3 PUFA) appeared to influence the changes of fatty acid composition of blood in the bodies of children with nephrotic syndrome. Supplementing the diet with omega-3 fatty acids tended to reduce the quantity of triacylglycerols (p<0,06). The increase in the eicosapentaenoic/arachidonic acid ratio showed that fish oil is useful as a supplement reducing the aggregation of platelets. Treatment with fish oil, when patients received 6 ml/d, was safe and had no serious adverse effect