To evaluate the relationship of central corneal thickness to the changes in intraocular pressure (IOP) in the sitting and supine position. Observational case-control study. The study group included Primary open-angle and chronic angle closure glaucoma patients. The control group consisted of patients without glaucoma seen for their routine eye examination. Central corneal thickness was measured by ultrasound pachymetry. Patients were then randomized to IOP measurement by Tonopen either sitting or supine after maintaining that position for 5 min. The position was then reversed and IOP measurements taken again after 5 min. Main outcome measure was change in IOP. One hundred and eighty-two eyes (90 in cases and 92 in controls) were examined. The mean CCT was 538.11 ± 37.17 μm in the study group and 545.34 ± 36.01 μm in the control group (P = 0.185). The mean IOP in the sitting position was 19.54 ± 5.39 mmHg in cases and 14.82 ± 4.01 in controls (P < 0.001). The mean IOP in the supine position was 20.51 ± 5.48 mmHg in cases and 16.02 ± 3.24 in controls (P < 0.001). Mean IOP change from sitting to supine was statistically significant in both groups (P < 0.001 for both). Postural change was greater in cases than controls (P = 0.020). There was no correlation between postural IOP change and CCT in cases (r = 0.143, P = 0.180) and controls (r = 0.096, P = 0.362). Postural IOP change is greater in glaucoma patients than non-glaucomatous patients. There was no correlation between postural IOP change and CCT.