Diabetes is a common metabolic disorder affecting the entire body with high morbidity and mortality worldwide. The major complications related to diabetes are mostly due to the macrovascular and microvascular bed impairment due to metabolic, hemodynamic and inflammatory factors. However, studies over the past decades have added also the lung as a target organ in both type 1 and type 2 diabetes. Diabetes has always been addressed as a major comorbidity conditioning the disease behaviour and the natural history of several respiratory diseases. Increased interest has recently focused on the pathophysiology of the metabolic glycaemic disorder and the respiratory diseases suggesting a similar background shared by the two conditions. The true relationship between pulmonary diseases and diabetes mellitus has not been clarified, this review aims to summarize the link between diabetes and coexisting respiratory diseases such as asthma, chronic obstructive pulmonary disease, respiratory infections, cystic fibrosis, lung cancer and obstructive sleep apnea from a pathogenetic and therapeutic point of view.