The objective of the study was to assess the composition of fatty acids including the content of unsaturated fatty acids showing a trans configuration, in 20 various cakes available on the market in the city of Olsztyn. The determination procedures were carried out using a GC method in a 100m capillary column with a CP Sil 88 phase. In the cakes investigated, the fat content ranged from 4.51 to 32.66 %; those cakes were characterized by a different content of fatty acids. The per cent content of saturated fatty acids in the fat of the products ranged from 10.55 to 50.20 %, the per cent content of monounsaturated fatty acids ranged from 37.20 to 63.13 %, and of the poly-unsaturated fatty acids: from 5.63 to 36.28 %. The trans isomers were present in the fat in all cakes studied.