- Statins are a group of drugs designed to lower cholesterol by inhibiting the enzyme HMG-CoA reductase. Statins have been shown to exhibit anti-inflammatory effects and have been suggested to be effective in some respiratory diseases. The aim of this review is to describe possibly mechanism of actions and effects of statins in respiratory diseases. Statins effects in respiratory diseases have been suggested to be related to decreases anti-inflammatory cells and proteins, decrease adhesion and migration of inflammatory cells, reduction of oxidative stress in the lung and anti-fibrotic properties. In asthma and COPD, statins have been suggested to have some synergistic effect with bronchodilators and antiinflammatory drugs. In scleroderma, anti-fibrotic, immune-modulating, and vasodilatory effects of statins are potentially beneficial as have been demonstrated by some studies. Statins have been shown to decrease TGF- β which is one of the key mediators in bronchiolitis obliterans but clinical investigation is still needed to show this effect in vivo. Clinical trials have failed to show beneficial effect of statins in idiopathic pulmonary fibrosis and in hypersensitivity pneumonitis and organizing pneumonia statins have been even suggested to be a cause. More investigation is needed for understanding the full clinical effects of statins in respiratory diseases.