The effect of partial substitution of La by Ca and Sr in the catalytic activity of lanthanum cobaltite (LaCoO₃) was studied. Two series of La_1−xCa_xCoO₃ and La_1−xSr_xCoO₃ (x = 0, 0.2, and 0.4) reduced perovskites were prepared, characterized and evaluated in the succinic acid conversion at 200 °C and 6 MPa. The characterization results showed a larger Ca substitution in the La_1−xCa_xCoO₃ series, whereas carbonates as segregated phases up to x = 0.2 of Sr were obtained in the La_1−xSr_xCoO₃ series. In the Sr substituted perovskites, the oxidation of Co³⁺ to Co⁴⁺ neutralizes the electronic instability, whereas in the Ca substituted perovskites the presence of Ca²⁺ generates oxygen vacancies. The succinic acid conversion forms mainly succinic anhydride and 2-hydroxy-tetrahydrofuran by dehydration and hydrogenation processes. The highest initial rate of the reduced LaCoO₃ was attributed to the smallest Co crystal size with no segregated phases, compared to substituted catalysts.