Fatty acid and sterol content of oil from nuts (cv Tonda di Giffoni) affected by two different biotic damages were characterized. Hazelnuts were sorted by a visual inspection of the kernels in three different samples (cimiciate, apparently healthy and moldy). The oil was extracted and analyzed by gas–liquid chromatography coupled to a flame ionization detector for fatty acid and sterol composition. The higher level of total polyunsaturated fatty acids (PUFA) in cimiciato oil compared to apparently healthy nuts was associated with the decrease in total monounsaturated fatty acids, resulting in a higher unsaturated/saturated acid ratio, while the PUFA content in moldy nut oil was lower than in apparently healthy nut oil. In both damaged samples, the appearance of four new chromatography peaks could be due to the presence of hydroperoxides, as proved by carrying out a TLC analysis. The overall phytosterol …