Conductivity, structure and thermochemical stability of compositions in the following series (100-x) La0.6Sr0.4CoO 3±δxCeO2 (LSCC), (100-x) La 0.8Sr0.2MnO3±δxCeO2 (LSMC) and (100-x) La0.95Ni0.6Fe0.4O 3-δxCeO2 (LNFC), where x=0, 2 and 10 mol%, were studied. CeO2 has slightly higher solubility limit in La 0.6Sr0.4CoO3±δ and La 0.8Sr0.2MnO3±δ compared to La 0.95Ni0.6Fe0.4O3-δ, forming LSCC2 and LSMC2 single phase solid solutions. All compositions containing more than 2 mol% ceria were two phase and consisted of a perovskite constituent with rhombohedral structure and ceria with cubic structure. Small additions of CeO2 influence the conductivity of the modified perovskites in a different way. Conductivity in the LSCC series dramatically decreased. Adding up to 10 mol % CeO2 slightly changed the total conductivity in the LSMC series in spite of the presence of the secondary phase. The conductivity of the perovskites as a function of oxygen partial pressure (0.21-10-4 atm) is discussed.