The paper presents an example of qualitative and quantitative application of a method for assessing component importance of a reliability structure in the case of a complex technical system based on the example of the subsystem of a marine power plant, that is, a lube oil system for sealing a stern tube. An example of the importance of the analysis considered in terms of not only reliability but also safety (impact of a component failure on human, machine and the environmental safety). Safety is usually analyzed in terms of quality, so the approach of trying to combine quantitative and qualitative estimation has been called a qualitative and quantitative method. A two - criteria importance of components according to the reliability criteria and safety criteria have been determined. The directions for further research have been outlined.