Objective To explore the diagnosis and treatment of critically ill patients suffering from obstructive sleep apnea-hypopnea syndrome ( OSAHS) . Methods Critically ill patients with OSAHS admitted in intensive care unit from January 2003 to December 2007 were retrospectively analyzed. Results Seventy-nine critically ill patients were diagnosed as OSAHS. The initial diagnosis of OSAHS was made by history requiring, physical examination, and Epworth sleepiness score evaluation. The final diagnosis was comfirmed by polysomnography thereafter. Base on the treatment of primary critical diseases, the patients were given respiratory support either with continuous positive airway pressure ( CPAP) or with bi-level positive airway pressure ventilation ( BiPAP) . Two cases died and the remaining 77 patients were cured anddischarged. Conclusions Timely diagnosis of OSAHS is important to rescue the critically ill patients. Respiratory support combined with treatment of primary critical diseases can improve the outcomes of these patients.