Objective To study the curative effect of continuous positive airway pressure (CPAP) on elderly patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) complicated with diabetes mellitus. Methods Eighty patients with OSAHS and diabetes mellitus were included and randomly divided into treatment group (n=40) and control group (n=40). The control group was given conventional treatment including diabetes diet and hypoglycemic drugs. The treatment group was given Futong ST-25 continuous positive airway pressure (CPAP) ventilation besides the conventional treatment. The serum levels of fasting blood glucose (FBG), two-hour postprandial blood glucose (2 hPG), insulin, sleep apnea hypop-nea index (AHI), low oxygen saturation (LSpO2) and the longest apnea time were monitored before and after treatment in two groups. Results After four-week treatment, values of FPG, 2 hPG, AHI and the longest apnea time were significantly lower in treatment group than those in control group (P < 0.01), but values of insulin, two-hour postprandial insulin and LSpO2 were significantly higher in treatment group than those in control group (P<0.01). Conclusion CPAP therapy can effec-tively decrease blood sugar level and improve AHI, LSpO2 and the longest apnea time in elderly patients with OSAHS compli-cated with type 2 diabetes.