Oil filtration and wear of hydraulic components depend on the particle properties. Current knowledge about particles is not sufficient to determine their effects precisely. With the aim of analyzing real and test particles, we have developed a method for extracting real particles from hydraulic filters. From both we have produced preparations for microscopy with optical and electron microscopes, which have proven to be better. The analysis showed differences in the particle shape and their material properties. They also showed that separate filter layers have different effects on oil filtration.