The aim of the study was to determine the influence of fatty acids sources on their metabolism in the liver and subcutaneous fat. Four iso-energetic and iso-protein diets with different ratio of PUFA/SFA and C 18:2 n-6/C 18:3 n-3 obtained by changing part of the diet energy with plant oils (linseed or rapeseed), tallow or fish oil, were given to pigs from 60 to 105 kg body weight (BW). Pigs were slaughtered at 105 kg BW. The content of fatty acids in the liver and subcutaneous fat per 100 g tissue and the activity (index) of Δ4- and Δ9-desaturase and elongase were determined. It was assumed that replacing part of energy of the diet with energy from different fatty acids of dietary oils will differ activity of enzymes in the investigated tissues and allow to determine in which the metabolism is more intense. Replacement of the part of the energy diets with energy from saturated (SFA), monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA), improved those feeds in the quantity/quality of these fatty acids and increased their proportional content, however, more in the subcutaneous fat than in the liver. Kind of diet had no influence on weight and fat content of the investigated tissues. Irrespective of the applied diet, a lower activity of Δ9-desaturase but higher activity of Δ4-desaturase and index of elongation were detected in the liver rather than in the subcutaneous fat. Results showed that they yield of elongation of the carbon chain of fatty acids and transformation of long-chain fatty acids is higher in the liver, however stronger transformations of SFA and MUFA take place in the subcutaneous fat.