Abstract <p>The structural features and some properties of aluminates of the composition LnAlO₃ (Ln = La, Ce, Pr) are studied. All three aluminates obtained at the final calcination temperature of 900°C have a cubic perovskite structure. In Ce-containing systems, along with it, a highly dispersed CeO₂ phase with a cubic fluorite structure is observed. The cubic perovskite structure is retained upon modification of La and Pr aluminates by substituting 10 at % of Ln³⁺ ions with Ca²⁺ ions; in this case, the unit cell parameter decreases due to the smaller radius of the Ca²⁺ ion compared to Ln³⁺, which indicates isomorphic substitution of Ln³⁺&#xa0;→&#xa0;Ca²⁺. The catalytic properties of the obtained systems in high-temperature oxidation of methane were studied. The analysis of the relationship between the surface properties studied by X-ray photoelectron spectroscopy and the catalytic properties of La and Pr aluminates allows us to conclude that point defects (presumably O^– oxygen radical ions) participate in the production of C₂ hydrocarbons, a process called oxidative coupling of methane (OCM). In the case of praseodymium aluminate, this mechanism is supplemented by a redox cycle occurring due to the oxidation-reduction of praseodymium ions (Pr³⁺ ⇌ Pr⁴⁺) on the surface of the samples. As a result, samples of similar composition (not modified and equally modified with calcium) based on praseodymium aluminate are significantly more effective as catalysts for the OCM process. Ce-containing samples are unstable under methane oxidation conditions; they decompose with the release of the CeO₂ phase and have very low selectivity for C₂ hydrocarbons. The conditions for a correct comparison of the efficiency of oxide catalysts for the OCM process are determined.</p>