['Smoking parents are the main source of passive smoke exposure in childhood. Only few studies have assessed the effect of maternal or paternal cigarette smoke exposure in childhood on the development and severity of COPD.', 'We recruited n = 251 COPD-patients, n = 113 were clinically stable (no exacerbations for up to 24 years backdated from the day of interview), and - according to their history - n = 138 had more than one exacerbation during this time period. All COPD-patients were interviewed by a physician using a structured questionnaire on main health outcomes, social status, smoking history of their parents and themselves. Furthermore, pulmonary function was measured, and concomitant lung diseases were excluded.', 'Both COPD groups were comparable in age, gender, smoking history at the beginning of the disease, and cigarette pack-years smoked. Patients whose mothers smoked during childhood had poorer lung function values: FEV (1) 45.2 % vs. 54 % (p = 0.037). Non-smoking patients with a history of maternal smoking had a 7-times higher exacerbation rate compared to patients without passive smoke exposure (p = 0.073). Paternal cigarette smoke exposure had no effect.'] Does [ Parental smoking and passive smoke exposure in childhood promote the COPD exacerbation rate ]?