Chronic obstructive pulmonary disease (COPD) has been traditionally considered a self-inflicted disease caused by tobacco smoking. Current available evidence, however, indicates that the pathogenesis of COPD needs to consider the dynamic and cumulative nature of a series of environment (including smoking plus other exposures)-host interactions that eventually determine lung development, maintenance, repair, and aging. By doing so, these factors modulate the trajectory of lung function of the individual through life and the odds of developing COPD through different routes, which likely represent different forms of the disease that require different preventive and therapeutic strategies.