Clinic-based retrospective case-control study. OBJECTIVES: To compare continuous positive airway pressure (CPAP) requirements between patients with tetraplegia and able-bodied patients with obstructive sleep apnoea (OSA). SETTING: Melbourne, Australia. METHODS: Diagnostic and CPAP titration polysomnograms of 219 able-bodied, and 25 patients with tetraplegia and OSA were compared for apnoea hypopnoea index (AHI) and CPAP levels required to effectively treat OSA. Demographics and body mass index (BMI) were obtained for each patient. ASIA score and injury date were obtained for patients with tetraplegia. RESULTS: There was no significant difference in AHI (P=0.102) between the two groups; however, able-bodied patients were significantly older (P=0.003), required significantly higher levels of CPAP to control their OSA (P<0.001) and had higher BMIs (P=0.009) than patients with tetraplegia. In the tetraplegia group, there was no significant correlation between AHI and effective CPAP (r=0.022, P=0.92) or between AHI and BMI (r=-0.196, P=0.35). There was a significant correlation between effective CPAP and BMI (r=0.411, P=0.041). Among able-bodied patients, over two-thirds (68.8%) required 10-16 cm H(2)0 to control their OSA and nearly one-third required over 16 cm H(2)0. In contrast, over two-thirds (68.8%) in the tetraplegia group required less than 10 cm H(2)0 of CPAP to control their OSA. CONCLUSION: This retrospective study suggests that OSA patients with tetraplegia require significantly less CPAP to treat their OSA at any given AHI than those who are able-bodied. This suggests that additional unknown factors may contribute to the high prevalence of OSA in tetraplegia.