Background: Sulfur mustard (SM) is a potent alkylating agent that targets several organs, especially lung tissue. SM exposure leads to serious changes in morphological structure of airway system, which is associated with chronic obstructive pulmonary deficiency following exposure to SM. With extensive progress and achievements in tissue repair through stem cells therapy, consideration of lung tissue has been increased due to the high prevalence of pulmonary problems. Several factors such as selection of cell types, required conditions for growth and proliferation of stem cells, and the process of entering into the body to repair damaged lung tissue are considered as the most important problems in this issue. Accumulating studies, both in animals and human with mesenchymal stem cells (MSC) support the hypothesis of therapeutic effects of these cells in various disorders. In this study investigators aimed to evaluate safety and potential efficacy of systemic MSC administration for treatment of chronic lung injuries in SM-exposed patients.