The purpose of this review is to summarise the existing knowledge of the relationship between exposure to en-vironmental tobacco smoke (ETS) and the development of chronic obstructive pulmonary disease (COPD). A possible causal relationship between ETS and COPD has long been suspected. Prenatal as well as postnatal ETS can reduce the lung function of the child permanently. Albeit the causality is multifactorial, new evidence has emerged since the Surgeon General's report from 2006 and suggests, that ETS is an independent and significant risk factor for developing COPD.