The existence of gaseous cobaltates of alkaline-earth metals was established in the present work by high-temperature mass spectrometry. Gaseous molecules: CaCoO₂, SrCoO₂ and BaCoO₂ have been found for the first time. On the basis of the measured constants of the equilibrium of gas-phase reactions the standard enthalpies of formation: (-149 ± 19) kJ · mol^-1, (-149 ± 20) kJ · mol^-1 and (-250 ± 16) kJ · mol^-1; and standard atomization enthalpies: (1251 ± 22) kJ · mol ^-1, (1233 ± 23) kJ · mol^-1 and (1353 ± 20) kJ · mol^-1 for CaCoO₂, SrCoO ₂ and BaCoO₂, respectively, have been defined.