In this book we highlighted: the basics of sleep physiology, milestone in development of knowledge about Sleep Disordered Breathing (SDB), detailed discussion of SDB: classification, epidemiology, pathophysiology, diagnosis and treatment. Also, this book reported different definitions and classifications of Diabetes Mellitus (DM). We have reviewed different literatures to find the links and pathophysiologic mechanisms in between SDB and DM and how each affects the other. Moreover, we have reviewed different methods of diagnosis of SDB used in many researches and studies in both topics. Finally, we have reviewed a number of studies involving different range of patient populations studying the relation between SDB and DM with or without insulin resistance, metabolic syndrome and effect of CPAP treatment on glucose and insulin state, as well as the effect of sleep duration and quality on glucose control in diabetic patients. To finally conclude our results and gives our recommendations.