Mesenchymal Stem cells (MSCs) are stromal cells that can be readily harvested from adult bone marrow and adipose tissue, but also umbilical cords. With respect to respiratory disease, the therapeutic potential of these cells lies in their paracrine effects which underlie their ability to enhance tissue regeneration and modulate immune responses. MSCs have been shown to be effective in a range of murine models of respiratory disease, and there are currently five clinical trials involving the administration of MSCs for respiratory diseases, including COPD and emphysema. This paper summarises the features of MSCs.