The paper addresses the topic on morpho-structural characterization of ultrafine particles generated in coal-based power plants, with special reference to Mintia-Deva power plant, Romania. The particles oxidic composition, concentration and size distribution were investigated. The concentration measurements have been performed based on light scattering for micro-sized particles and differential mobility analysis for nanometric scale. The highest values of oxide component concentration have been registered in the coal powders sampled from the work places at breaking room and on conveying belts. The dust composition mainly consisted of silica, and also iron, aluminum, calcium and magnesium oxides, with more than 25% SiO2, 10% Al2O3, 4%Fe2O3.