Owing to their nature, fish lipids are highly susceptible to oxidation, especially to auto-oxidative processes. The degree of oxidation depends on many factors including the distribution of lipids in a muscle tissue. The objective of this study was to prove that various parts of farmed rainbow trout fillet differ not only in the content of lipids, but, also, in their technological usefulness, which may be characterized by the rate and extent of oxidative changes in lipids. It was evidenced that, as regards the fat content, the ventral part of rainbow trout fillet differed significantly from the other fish parts analyzed. Also, the differences were proved to exist between this ventral part of the trout fillet and the other fillet parts; those differences referred to: the dynamics of UV rayscatalyzed photo-oxidation of lipids, the composition of fatty acids, in particular the amount of docosahexaenoic acid (DHA). On the other hand, no statistically significant differences were reported in the initial total oxidation value (Totox) of lipids contained in the particularized parts of the rainbow trout fillet.