For decades, neurologic and pulmonary disorders have been associated to diabetes mellitus (DM) and more recently to obesity. Many studies have attempted to establish the association between sleep apnea and adult-onset DM. Growing evidence exists demonstrating the association between insulin-resistance and obstructive sleep apnea (OSA), as well as sleep-disordered breathing (SDB) in non-obese diabetic patients with autonomic neuropathy. In patients with DM, two types of sleep disorders can be found; upper airway resistance syndrome and sleep apnea. The later apnea can be central, obstructive or mixed. In either case, a decrease in the oxygen saturation will ensue, and sleep arousal will occur. The diagnosis of sleep apnea in patients with DM is mainly done by obtaining a good history and physical examination. The main symptoms in the patient with sleep apnea include excessive daytime sleepiness (frequently seen in situations which are not mentally demanding). Effective continued positive airway pressure (CPAP) treatment show clinical improvement in symptoms as well as in insulin sensitivity. The relation between SDB and DM can have significant impact on the overall health of the patient.