Decreases in glial cell density and in GFAP mRNA in the anterior cingulate cortex have been reported in schizophrenia, bipolar disorder and major depressive disorder. Our study examines astrocyte and oligodendrocyte density in the white and grey matter of the subgenual cingulate cortex, and at the midline of the genu of the corpus callosum, in schizophrenia, bipolar disorder, depression and normal control cases. Serial coronal sections were stained with H and E for anatomical guidance, cresyl haematoxylin for oligodendrocyte identification and GFAP immunohistochemistry for astrocyte identification. Oligodendrocyte and astrocyte density was measured using systematic anatomical distinctions and randomised counting methods. A significant decrease in astrocyte density was observed in schizophrenia compared with normal controls in the cingulate grey matter, cingulate white matter and the midline of the corpus callosum (p = 0.025). Bipolar disorder and depression cases showed no significant changes in astrocyte density. Oligodendrocytes did not show any changes between diagnostic groups. In subgenual cingulate cortex, the ratio of oligodendrocytes to astrocytes was decreased between the controls and the three disease groups, suggesting a specific glial cell type specific change in schizophrenia.