The characteristics of a Q-space focusing configuration are given. The procedure to get inverse space conditions is given also. Both the diffraction and inelastic scattering are considered. For the neutron diffractometry both instruments with one crystal monochromator and with two crystals monochromators are taken into consideration. The time of flight diffractometers both for a pulsed neutron source and a steady state one is considered also. For inelastic scattering the inverse space focusing conditions for triple axis spectrometers are givene line-width.