Fatty acids composition of the adipose tissue from the belly and dorsal and lumbar fat of Iberian pigs carcase was studied in order to choose the most appropriate section of the animal to obtain the samples. Pigs were subjected to two feeding systems: "montanera" and "commercial feed". The statistical analyses showed that there were no significant differences between feeding x section. Therefore, the dorsal fat was chosen as the easiest to obtain from carcase. A study on the fatty acids composition of adipose tissue was carried out in the dorsal fat, considering feeding as the only variation factor and employing three groups of animals which were fed with "montanera", "commercial feed" and "montanera + commercial feed". Even though the results obtained allow a total or partial diferentiation of the three types of feeding by the lauric, palmitic, oleic, linoleic and linolenic acids, only cannot be used commercially as diferentiation variables.