Modern cylinder liner manufacturing processes such as MMC casting, laser honing and laser exposure allow a design of cylinder liner surfaces to meet common development goals like less air pollution and reduced fuel and oil consumption. These goals are reached by aimed insertion of function-relevant structures on the micrometre scale into the surface. Because of these function-relevant structures, the commonly used 2D roughness parameters like Ra and Rz cannot describe the functional behaviour of these surfaces. To describe these surfaces it is necessary to extend the roughness evaluation into the third dimension: z = z(x, y). This paper proposes a 3D roughness evaluation method based on morphological algorithms like the watershed transform to detect and separate the function-relevant structures. Every detected structure is described by a set of structural parameters. Statistical combining of these structural parameters provides a functional characterization of the complete measured surface. The possibilities provided by this flexible method of surface evaluation are shown with a calculation of honing angles.