Amporphous WN0.3 nanoparticles were generated by pulsed excimer ablation of tungsten in a N2 ambient at atmospheric pressure. Size distributions and concentrations were monitored by dynamic mechanical analysis (DMA) and condensation particle counter (CPC) with different laser parameters and sport sizes. It was found that the fast desorptive part for which a thermal process for material removal was ruled out and the 'real' ablation gave rise to different types of size distributions.