Soil scientists often examine the soil structure and macroporosity by observing sections using a variety of microscopic and photographic techniques. The most frequent parameters used in the image analysis to characterize pores are: shape factors (like circularity, compactness, elongation, etc.), size parameters (surface area, Crofton perimeter, etc.) and arrangement eg MBR (minimum bounding rectangle) angle. The pores are usually classified according to equivalent pore diameter estimated from the area of pores. This paper presents a proposal of a method for separating macropores according to their real diameter. Aphelion, the image analysis system, was used to prepare a procedure for splitting soil macropores and dividing them into selected fractions according to the diameter. The procedure was tested on porous and compacted soil samples which differ in their porosity, pore shape and size. The results show that the detection of macropores according to the real pore diameter is suitable for the characterization of the actual state of soil macroporosity, especially in porous soils with continuous branching macropore system.