The objective of this paper was to assess the quality of lipid fraction, especially of the trans isomers of unsaturated fatty acids content, in the fat of 15 confectionery products and of 5 potato chips available on the Warsaw market. The content of groups of fatty acids in the fat of the products investigated was determined by gas chromatography. Trans isomers were found in the fat of all the samples. Their content levels ranged from 0.1 % to 12.1% in the confectionery products, and from 1.1 % to 1.8 % in the total fat of potato chips. The content of saturated fatty acids was from 19.2 to 72.4 %.