The effect of the externally introduced rf magnetron plasma on the particle size distribution on films deposited by pulsed laser ablation is investigated. A cw low energy magnetron rf plasma is sustained between the target and the substrate during the laser ablation deposition process. The ablated droplets can be negatively charged and filtered by the plasma. For Si and Al target ablation, the filtering efficiency of the inert Ar plasma is about 20%, and is independent of the ejected particle size in our system. If oxygen is introduced into the plasma to deposit oxide thin films, the oxidation of the target surface in the reactive plasma changes the size distribution of the ejected particles, and largely reduces the average size of the ejected particles.