Objective: To investigate the function of vascular endothelial cells (EC) and the plasma levels of nitric oxide (NO) and endothelin (ET) in elderly Chinese patients with obstructive sleep apnea hypopnea syndrome (OSAHS) and its association with coronary heart disease (CHD). Methods: Elderly simple snorers (n = 31) with neither OSAHS nor CHD were randomly selected as the control group; 45 elderly patients with moderate or severe degree of OSAHS were recruited as the OSAHS group, which were further divided into two subgroups, CHD subgroup (16 patients) and non-CHD subgroup (29 patients). The changes of plasma concentrations of NO and ET were compared between the groups. Results: Compared with the control group, in the OSAHS group there was a significantly lower NO level (27.7 ± 9.2 μmol/L vs 61.9 ±13.5 μmol/L, P < 0.01), higher ET level (58.1 ± 14.2 ng/ml vs 34.8 ± 8.2 ng/ml, P < 0.01), and lower NO/ET ratio (0.47 ± 0.18 vs 1.72 ± 0.97, P < 0.01). The incidence of CHD in the OSAHS group was 35.6%. Comparison between the control group and non-CHD OSAHS subgroup showed that the decreased NO level (35.5 ± 9.4μmol/L), increased ET level (47.5 ± 11.1 ng/ml) and declined the NO/ET ratio (0.75 ± 0.13) in non-CHD subgroup were statistically significant (P < 0.05). This difference was more significant between the control group and CHD OSAHS subgroup (P < 0.01). Comparison between the two OSAHS subgroups indicated that there was a significantly lower NO level, higher ET level and more declined NO/ET ratio in those with OSAHS and CHD than in the OSAHS without CHD subgroup (all P < 0.05). Conclusion: Vascular endothelial function was significantly impaired in elderly Chinese patients with OSAHS, especially in those with both OSAHS and CHD. Dysfunction of the vascular EC may be one of the causes of CHD in OSAHS patients.