Neutron powder diffraction is extensively used for the development and fundamental understanding of metal hydrides. In this chapter we will first present the basic principles of neutron diffraction. This will be followed by a discussion about the two main neutron sources used for diffraction experiments: reactors and spallation sources. Analysis of diffraction patterns by Rietveld refinement will be discussed next: we will expose the principle of the method and the significance of various parameters to be refined. The special case of locating the hydrogen using neutron powder diffraction will be discussed in a separate section. The final section is a presentation of a few selected examples of the application of neutron powder diffraction to metal hydrides.