We have used neutron powder diffraction to make a comprehensive study of the crystal structure in Pr2Fe17 nanocrystalline compounds. These nanostructured materials have been obtained by high-energy ball milling from an arc-melted bulk polycrystalline alloy. The Th2Zn17-type rhombohedral crystal structure of the starting bulk alloy is maintained after milling for 10 and 20 hours. The studied alloys are ferromagnetic below T-C = 286+/-1 K (bulk) and T-C approximate to 300+/-20 K (milled). These materials exhibit strong magneto-volume anomalies below T-C, such as a negative coefficient of thermal expansion (alpha(V) approximate to -30 x 10(-6) K-1).