Adiponectin is a predominantly anti-inflammatory protein produced by adipose tissue with possible signalling activity in the lung. It is increasingly associated with inflammatory pulmonary diseases, such as asthma and chronic obstructive pulmonary disease (COPD), and in critical illness. Although mouse studies indicate causative associations between adiponectin and asthma and COPD, the human literature in this regard is inconclusive. Some, but not all, studies demonstrate that serum adiponectin concentrations are inversely associated with asthma prevalence among premenopausal women and peripubertal girls. On the other hand, serum adiponectin concentrations are associated with lower asthma severity among boys but greater severity among men. Further, case-control studies demonstrate higher systemic and airway adiponectin concentrations in primarily male COPD patients than controls. Systemic adiponectin is positively associated with lung function in healthy adults but inversely associated in studies of male subjects with COPD. Murine and human studies further show contradictory associations of systemic adiponectin with critical illness. Higher premorbid systemic adiponectin concentrations are associated with improved survival from sepsis in mice. On the other hand, higher systemic adiponectin concentrations on day 1 of critical illness are associated with lower survival in critically ill patients with respiratory failure. In the absence of adequate longitudinal data, it is not possible to determine whether the adiponectin derangements are the consequence or the cause of the disease studied. Future research will determine whether modulation of adiponectin, independent of BMI, may be helpful in the prevention or treatment of asthma, COPD or critical illness.