Pursuant to Directive 2000/36/EC, it is possible to add a fat other than cocoa fat to chocolate products; its addition can amount to 5 % of the general content of cocoa mass. The main objective of this paper was the analysis of fats in some selected dark chocolates available on the Polish market. After the qualitative and quantitative analysis of fats in the products investigated, it was also attempted to assess their authenticity. The analysis of the composition of fatty acids and sterols, especially of the content of basic acids, i.e. of palmitic, stearic, linoleic, and oleic acids, constituted the basis for either confirming or negating the authenticity of the products under investigation. Based on the investigations performed, it was proved that four from among all the chocolates examined significantly differed from other products. In the majority of the chocolates, the content ratio between the palmitic and stearic acids proved the fact that substitutes were applied instead of cacao or plant fats.