In a random sample of more than 30 000 Swedish adults, e-cigarette use was most common among current smokers, and the prevalence of respiratory symptoms was highest among the current smokers who also used e-cigarettes. [...] During the last 30 years, the proportion of smokers has steadily decreased in Sweden, which has contributed to a decreased prevalence of respiratory symptoms and chronic obstructive pulmonary disease (COPD) among adults, less exposure to environmental tobacco smoke, [...]