[Sr2O2]0.52CoO2obtained through high-pressure synthesis is a parent of misfit-layered cobalt oxides, such as [CoCa2O3]0.62CoO2or [MmA2O2+m]qCoO2in general. Our comprehensive X-ray absorption spectroscopy study shows that both [Sr2O2]0.52CoO2and [CoCa2O3]0.62CoO2possess mixed III/IV valence cobalt, but the average Co-valence is a little lower in the former. This is tentatively believed to be due to OHgroups replacing part of O2−ions in the [Sr2O2] layer block.