The objective of this research was to evaluate dietary behaviours of the patients from cardiologic clinics in Szczecin and to estimate their knowledge of the Mediterranean diet principles. The research was conducted using a method of 24-hour anamnesis. The polled group consisted of men (67 persons) and women (88 persons) aged above 26 years. Referring to the regular meals eaten by the polled, three factors were computed: content of nutrients contained in their meals, percentage rate of realizing the relevant nourishment norm, and energy provided with their meals. The received values were compared with the safe levels of nutrients as indicated by the relevant norms on proper nourishment. Additionally, the frequency of consuming certain products by the polled, according to the pyramid of healthy diet, was determined. Coefficients of losses occurring owing to technological and culinary processing procedures were also included. A “Dietetyk 2” software and ‘Exel’ package were applied. Furthermore, the impact of the diet applied on the biochemical parameters of the patients’ blood (total cholesterol concentration, HDL and LDL fractions, as well as triacylglycerols) was estimated. The research proved that the knowledge and use of Mediterranean diet principles among the polled was little. Average concentration levels of total cholesterol and LDL fractions in their blood were increased compared to the generally approved norms. A considerable number of patients suffered from dietdepending diseases and lipid disorders. Quite probably, it resulted from their improper dietary behaviours, i.e. from the fact that they usually ate meals rich in monosaccharides and in saturated fatty acids, but poor in fruit and vegetables. According to the research results, it was also found that their meals contained too little amounts of dark bread, milk and milk products, cereals, and rice; thus, their daily meals provided too little amounts of vitamins from the B, C, and D groups, and of calcium per day. The level of fish consumption was low, too. Moreover, it was found that all the polled showed a low physical activity level.