The article deals with the size distribution of aerosol particles in the range of 10 nm to 500 nm. The measurement was performed inside five primary schools in the South Moravian region from the 5.10.2014 to 21.1.2015. Average concentrations of nanoparticles and larger particles were consequently calculated for the assessed schools, as well as their mean diameter, surface area, approximate specific surface energy and approximate mass concentration per unit volume. Nanoparticles in the range from 10 nm to 100 nm made up 60-86% of the whole number of counted particles. Approximate mass concentration allocated to these nanoparticles was in the range from 3% to 6%. The parameters for specific surface of particles (SSA) and specific surface energy (SSE) were derived for the characterization of their importance in the full sample. The SSE of measured nanoparticles was estimated to be 6.0-7.21 J·cm-3, while for the particles in the range from 100 nm to 500 nm the estimated values were 1.7-1.88 J.cm-3. The relationship between the traffic intensity and number concentration of particles inside the tested primary schools was observed as well. While the correlation was low or slightly medium (RS = 0.36) for the particles larger than 100 nm, for nanoparticles in the range from 10 nm to 100 nm the correlation was middle or high (RS = 0.67). The trend of increasing of the number concentration of nanoparticles due to the traffic intensity was considerably discernible.