The lipid-lowering effect of a concentrated salmon oil, rich in n-3 fatty acids was tested as a supplement to the normal diet of 27 patients with high levels of cholesterol and/or triglycerides, during 2 months. The results of the study confirmed that addition of n-3 fatty acid to diets produced a reduction of plasma levels of lipids. The most significant reduction of plasma levels of lipids. The most significant reduction was observed in triglycerides in patients with high levels (from 295.8 to 219.8 mg/dl) (p = 0.001), as well as the whole group (from 231 to 180 mg/dl) (p = 0.002). At the same time, there was a reduction of cholesterol in all patients (from 295 to 268.4 mg/dl) (p = 0.001), including those whose cholesterol was higher (from 316.2 to 284.9 mg/dl) (p = 0.002). We concluded that the use of compounds rich in n-3 fatty acids showed an important plasma lipid-lowering effect, playing a significant role in hyperlipidemic patient control.