The objective of the study was to asses the effect of the production system on fatty acids (FA) composition of intra-muscular fat of three muscles (longissimus dorsi, semitendinosus, diaphragmae) from Simmental bulls. Bulls (n=8) were fattened either with maize silage and concentrates or on pasture. Grazing bulls showed a significant lower percentage of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA), but had higher percentage of polyunsaturated fatty acids (PUFA) and conjugated linoleic acid. The n-6/n-3 PUFA ratio was significantly lower (P<0.001) and the PUFA/SFA ratio was significantly higher (P<0.001) in muscles of grazing bulls. The lowest SFA percentage was found in semitendinosus (36.5±0.8) followed by longissimus dorsi (44.4±0.8) and diaphragmae (48.2±0.8) muscle. The percentage of PUFA and n-3 PUFA was the highest in semitendinosus muscle, while the n-6/n-3 PUFA ratio was similar in all three analysed muscles.