General formulas are derived for the shift in x‐ray diffraction maxima due to small distortions in simple cubic crystals. The special case of radial distortions due to lattice defects is considered in detail; it is found that the relative change in lattice constant computed from the shift in diffraction maxima is of the order of magnitude of the defect concentration and larger by as much as 100 percent than the linear expansion when the concentration of defects is of the order of one percent or less. A comparison is made of lattice constant, linear expansion, and density expected in crystals containing Frenkel defects, Schottky defects, orFcenters.