The six nanosized PrF3 samples were synthesized using two different chemical reactions and different time of hydrothermal reaction. The X-ray and HRTEM experiments showed high crystallinity of synthesized samples. For all samples the particles size distribution was obtained. It was shown, that precursors of chemical reaction have influence on the shape of synthesized nanoparticles. The size of nanoparticles depended on the time of hydrothermal reaction as much as roughly 10 nm per hour.