Layer oxides with formula AxMO2 where M stands for a transition element with two oxidation states or for a mixture of tetravalent and trivalent (or eventually divalent) elements are obtained for 0.5 ≤ x ≤ 1. The lattice is built up by sheets of edge sharing MO6 octahedra between which the alkali ions are inserted with trigonal prismatic or octahedral environment. Similar structures can be found among A2MO3 oxides, the alkali ions lying between sheets. The influence of the pressure on the stability of the various packings is discussed. Layer structures are also obtained for the compositions Li8MO6, Li7L□O6 and Li6In2□O6. Structures of these pseudo-2D materials are characterized by a packing of octahedral and tetrahedral sheets where the alkali ions and the vacancies are distributed. Transport properties of these materials have been studied.