Abstract Nanoparticles (NPs) were produced by ablating tungsten and boron-carbide (B 4 C) target materials in atmospheric pressure nitrogen ambient using ArF excimer laser pulses. The size distributions of the NPs formed during the ablation were monitored—within a 7–133 nm size window—by a condensation particle counter connected to a differential mobility analyzer. The laser repetition rate was varied between 1–50 Hz, and the fluence was systematically changed in the range of 0.5–15 J/cm 2 , for both materials, allowing a comparative study in an extended laser parameter regime. The multishot ablation threshold ( Φ th ) of B 4 C was determined to be ∼1.9 J/cm 2 for the laser used (ArF excimer, λ = 193 nm). Similarly to earlier studies, it was shown that the size distributions consist of mainly small nanoparticles ( Φ th . An additional broad peak appears (between 20 and 40 nm) above Φ th as a consequence of the thermally induced macroscopic ablation. Chemical composition of deposited polydisperse nanoparticles was studied by X-ray photoelectron spectroscopy showing nitrogen incorporation into the boron-carbide.