Obstructive sleep apnea (OSA) is a common disorder which is characterized by intermittent upper airway collapse occurring during sleep. It is well known that OSA often results in a wide range of comorbid disorders. I introduce here what OSA brings to the patients in neurologic department. Epidemiological studies have shown that OSA is associated with cognitive impairment, headache, metabolic syndrome, various cardiovascular diseases including hypertension, ischemic heart disease, arrhythmia, and stroke. Motor vehicle accident is not seemed to be related to a neurological condition but it can be also related in terms of excessive daytime sleepiness and decreased attention in patients with OSA. Obstructive respiratory events like apnea, hypopnea, and respiratory effort related arousal cause repetitive hypoxia, hypercarpnea, arousal, and decreased intrathoracic pressure. In turn, these can increase blood pressure, sympathetic activity, insulin resistance, and left ventricular wall tension. Consequentially, these processes can be considered as possible mechanism. Although further researches are needed to prove that OSA is independent cause of comorbid conditions, OSA especially in moderate or severe cases can develop and aggravate such conditions as risk factor. So we should know what OSA brings to us and pay attention whether OSA is combined in the patients whom we meet in neurological department.