Electron spin resonance spectra obtained on polycrystalline silicon produced by annealing of chemical vapor deposition silicon are investigated before and after plasma hydrogenation of the material. Before hydrogenation, two paramagnetic defects are observed, one of them remaining unidentified (g=2.0084). Hydrogenation decreases the total spin density, but the two defects are affected differently; the defect withg=2.0084 is more efficiently passivated. The results are discussed in terms of the inter‐ and intragranular nature of the paramagnetic defects and of hydrogen diffusivity in the polycrystal.