At the beginning of the 21st century obesity has become the leading chronic disease in the world. It is a major cause of morbidity mainly in the metabolic and cardiovascular areas. Moreover, it has progressively emerged as an important risk factor for respiratory diseases, a field that is often neglected. In this article, we reviewed the current understanding of the influence of obesity in adulthood on respiratory function, obstructive sleep apnoea-hypopnoea, obesity hypoventilation syndrome and asthma.