Obesity is known to be a major risk factor of a whole range of cardiovascular, metabolic and respiratory disorders. It has been recognised that the pattern of regional fat distribution plays an important role in the pre-disposition of obese subjects to certain obesity-related complications. Derangement of parameters of lung function is determined to a large extent by the quantity and distribution of excess body fat with its potential to interfere with the mechanics of pulmonary physiology. Clinical, laboratory and epidemiological observations have established links between obesity and several breathing problems including obstructive sleep apnoea, obesity hypoventilation syndrome and asthma. However, in many respects, the pathophysiology of these links is not fully explored. In this article, the impact of obesity on pulmonary physiology and its association with the above-mentioned clinical conditions is discussed.