The aim of the work is assessment of the possibility of increasing the thermal conductivity of the filled epoxy resins. The heat management in the electronic and power devices is a crucial issue. It is an important problem to be solved in order to prevent such devices from malfunction. The effective heat dissipation is thus one of the main challenging problems to be solved. The pure boron nitride micro-powders with different size distribution and surface modification, as well boron nitride mixtures with silica were used as the fillers for preparation of the epoxy resin composites. A representative set of filled epoxy samples has been prepared with the different content of the investigated fillers. The thermal conductivity measurements have been performed on these samples at the room temperature and SEM observations have been showed.