The aim of this work was to assess the respiratory related and auditory evoked potentials in obstructive sleep apnea syndrome patients and compare them to a group of controls during both wakefulness and sleep. This work was done on 10 obstructive sleep apnea syndrome patients and 10 controls. The results show similar responses to both types of evoked potentials during wakefulness in both obstructive sleep apnea patients and the controls. However there were damped responses to respiratory related evoked potentials in the patient during sleep as compared to the controls, which was not the case using the auditory evoked potentials. These results point out that obstructive sleep apnea patients have a damped cortical response to respiratory related evoked potentials that is stimulus-specific and sleep state dependent.