Structural and defect structural aspects of Lithiated layer-structured transition-metal oxides with the alpha-NaFeO2 structure will be discussed in relation to stability and electrical behaviour. Emphasis will be put on anti-site disorder in LiNiO2. The defect structures of lithiated spinel-structured LiMn2O4 are quite dependent on the Li/Mn ratio and the dopants. Even defect clusters have been proposed to occur in non-stoichiometric LiMn2O4. It will be shown that important information on the defect structures can be obtained from magnetic and electron spin resonance (ESR) experiments on lithium-deficient Li1-xMn2O4 and lithium-excess spinel Li1+dMn2-dO4. The number of unpaired electrons provides information on the distribution of electrons over the t(2g) and e(g) orbitals. The Curie temperature provides information on cation-cation and cation-anion-cation interactions.