Abstract: The aim of this study was to analyse how changing the processing parameters of WC-Co powder affects its properties. The powder mixture properties were evaluated by technological tests firstly and then the results were than compared with properties of SD251 stainless steel powder which is commonly processed by the technology of selective laser melting (SLM). Different laser powers and laser spot feed rates were used for different samples. As a result, different values for the applied energy density Ev were obtained. The changes in the density, porosity and changes in the chemical and structural compositions of the printed samples were then evaluated using light and electron microscopy. This evaluation was supplemented by X-ray diffraction analysis of the phase composition and evaluation of mechanical properties using hardness testing. These experiments allowed us, for example, to determine the dependence of the density of the samples on the applied energy Ev. The maximum density of the printed samples was about 70%. In addition, metallographic analysis and X-ray diffraction analysis revealed the development of the eta phase in the specimens, and how changing the parameters changes the type and number of pores in the volume of the printed samples.