Obstructive sleep apnoea syndrome (OSA) is a disease very frequently occurring in people with type 2 diabetes, that significantly increases cardiovascular morbidity and mortality. In a number of studies, OSA has been identified as an independent risk factor for the development of insulin resistance, glucose intolerance and type 2 diabetes mellitus. Disorders of glucose homeostasis in patients with OSA are probably mediated by chronic intermittent hypoxia and/or sleep fragmentation through activation of the sympathetic nervous system, the hypothalamic-pituitary-adrenal stress axis, pro-inflammatory paths or oxidative stress. Despite the high prevalence of OSA among patients with type 2 diabetes as well as the proven benefit of the continuous positive airway pressure (CPAP) therapy on reduction of mortality, most patients with OSA remain undiagnosed. Active OSA screening should therefore be performed in all patients with type 2 diabetes, ideally through home monitoring of oxygen saturation and breathing during sleep. Although the effect of CPAP therapy on the improvement in diabetes control (decrease in glycated hemoglobin) has not been clearly proven in patients with type 2 diabetes so far, promising outcomes have been observed during the treatment of patients with prediabetes.Key words: CPAP - diabetes mellitus - glycemic control - intermittent hypoxia - obstructive sleep apnoea - screening - sleep fragmentation.