Layered double hydroxides (LDH) are interesting materials due to their high absorption and catalytic properties. Their applications in environment, agriculture and pharmaceutical fields are becoming widely important. The interlayer and intralayer cation ordering on layered double hydroxides of Mg:Al 2:1 and Zn:Al 2:1 are studied by means of different ordering models at Density Functional Theory level. The cation ordering in LDH is interesting for monitoring the synthesis of these solids and for the applications of LDH, however it is difficult to determine experimentally. We have explored several ordering arrangements of the cation distribution in Mg:Al 2:1 and Zn:Al 2:1 LDH and the effect of these cation arrangements on some crystallographic and spectroscopic properties.