This work focuses on an assessment of the real fiber and matrix volume ratios of unidirectional fiber composites that can be used for the design of corresponding numerical models on the micro-scale. Samples with polished cross-sections were prepared from three composite plates and they were previously analyzed using scanning electron microscopy (SEM). All the plates were manufactured from the same prepreg material using autoclave technology. Each plate consisted of a different number of plies. Images of the various parts of the composite cross-sections obtained with SEM are analyzed using several image-processing techniques programmed in Matlab, its Image Processing Toolbox, and C code. The results of this analysis are the center positions and radii of all fibers within the image. The fiber and matrix volume ratios are determined subsequently and mutually compared for different locations across the plates' thicknesses. Keywords: composite, unidirectional, micromechanics, constituents, image, detection, microscopy, cross-section Delo je osredoto~eno na oceno realnih vlaken in volumenskega dele`a v osnovi, v enosmernih kompozitih iz vlaken, ki jih je mogo~e uporabiti za postavitev ustreznih numeri~nih modelov na mikropodro~ju. Pripravljeni vzorci, s poliranim presekom, iz treh kompozitnih plo{~, so bili pregledani s pomo~jo vrsti~nega elektronskega mikroskopa (SEM). Vse plo{~e so bile izdelane iz enakega, v avtoklavih izdelanega, predimpregniranega materiala. Vsaka plo{~a je bila sestavljena iz razli~nega {tevila plasti. Posnetki razli~nih delov preseka kompozita, dobljeni s SEM, so bili analizirani z ve~tehnikami za obdelavo slik, programiranimi v Matlab, Image Processing Toolbox in C-kodo. Rezultati teh analiz so pozicije sredine in radiji vseh vlaken na posnetku. Pozneje so bili dolo~eni, in medsebojno primerjani, volumenski dele`i vlaken na razli~nih lokacijah preko debeline plo{~e.