Abstract： Background Adiponectin, secreted by adipocytes, has been found to be associated with diabetes, obesity and some cardiovascular diseases. Obstructive sleep apnea hypopnea syndrome (OSAHS) is also closely related to obesity and easily complicated with diabetes and some cardiovascular diseases. This study was carried out to explore the change of serum adiponectin level in patients with OSAHS.Methods Polysomnography was performed in 71 patients with OSAHS (OSAHS group) and 26 simple obese controls (control group). The two groups had no significant difference in age and body mass index (BMI). Radioimmunoassy was used to test serum adiponectin level.Results Serum adiponectin level was significantly lower in OSAHS group [(5.03±1.01) mg/L] than that in the control group [(7.09±1.29) mg/L, P<0.05]. The differences between two groups were independent of gender. In OSAHS groups, serum adiponectin levels were negatively correlated with apnea hypopnea index (AHI) (r=-0.78, P<0.01), BMI (r=-0.13, P<0.05), waist circumsference (r=-0.36, P<0.01), and neck circumference (r=-0.42, P<0.01), but positively correlated with the minimal pulse oxyhemoglobin saturation (r=0.48, P<0.01). Conclusion OSAHS may contribute to the decrease of serum adiponectin level independent of obesity.