Abstract Stomata characteristics of two extinct conifer Cheirolepidiaceae species, Pseudofrenelopsis gansuensis and Pseudofrenelopsis dalatzensis , were used to reconstruct the atmospheric carbon dioxide concentration levels during the late Albian of the Cretaceous. A sequence of fossil samples was collected from five beds in the Dalazi Formation in the Zhixin and Luozigou basins of Jilin Province, northeastern China. The stomatal index was used to estimate the palaeo- p CO 2. The average stomatal index value of the two species was 4.1 and the atmospheric CO 2 content was c. 1200 ppmv by the average of Recent standardization and Carboniferous standardization. During the short interval from 104.8 ± 0.5 Ma to 104.0 ± 0.4 Ma in the late Albian, the atmospheric CO 2 content presents a decreasing tendency, with the highest value being c. 1300 ppmv in the Luozigou Basin. In addition, the higher atmospheric CO 2 values of the late Albian are likely linked to a ‘greenhouse climate’ during the time of Oceanic Anoxic Event 1c (OAE1c).