This study was aimed at determining lipid content, fatty acid composition and trans isomers content in fat extracted from cereals and cereal bars. Cereals and cereal bars were analyzed by gas chromatography. Analyses showed that they were characterized by a diversified content of fat and composition of particular groups of fatty acids (saturated SFA, monounsaturated MUFA and polyunsaturated PUFA). Only oat flakes turned out to be a good source of PUFA (38.83% of total fatty acids). The remaining products contained more SFA (mean: 45.12% and 47.73% in cereals and 63.31% in cereal bars) than PUFA (mean: 12.24% and 16.73% in cereals and 7.83% in cereal bars). Lipid of all examined products contained trans isomers of C18:1 and C18:2 acids. In lipids of cereals, the total content of these isomers did not exceed 0.5% of the total fatty acids. A higher content of these isomers was found in cereal bars (0.45–3.15%).