OBJECTIVE: The purpose of this study is to evaluate the haemodynamic and respiratory effects of dexmedetomidine vs. propofol in patients with OSAHS during the drug-induced sleep endoscopy (DISE), and analyze simultaneously the electromyography of genioglossus muscle. PATIENTS AND METHODS: We conducted a study on 50 patients with OSAHS; patients were subjected to DISE with simultaneous polygraphic cardiorespiratory measurement and electromyography of genioglossus muscle. Patients undergoing DISE were divided in two groups: in Group A (19 M; 8 W) was administered propofol TCI and in Group B (16 M; 7 W) was administered dexmedetomidine TCI. RESULTS: In Group A, a mean minimal SpO2 decreasing of 3.7% (p=0.000) and a mean SpO2 decreasing of 1.6% (p 0.001) was noticed, while there was an increase in BP20 of 14.8% (p=0.000) and HR20 of 11.1% (p=0.000). In Group B, it was showed a decreasing of mean minimal SpO2 and mean SpO2 values, about 1.8% (p=0.000) and 1.1% (p 0.009) respectively, while there was an increase of BP20 and HR20, about 8.7% (p=0.000) and 8% (p 0.002), respectively. Despite EMG activity comparing spontaneous sleep with propofol-DISE, there is a statistically significative change for the amplitude (p=0.040) and an increase of 7.01% for the area under the curve (AUC). Comparing spontaneous sleep with dexmedetomidine-DISE induced one, there is only an increase of 25.87% in the AUC. CONCLUSIONS: A greater worsening of the cardio-respiratory basal values was noted after sleep induction with Propofol and same results were obtained confronting EMG of genioglossus muscle data.