Chronic obstructive pulmonary disease (COPD) is associated with high personal and societal burden and mortality. COPD is usually diagnosed during middle or late adult life, but the starting point for a 'COPD career' may be found earlier in life, during adolescence: first, because of smoking initiation and subsequent accumulation of risk, and second, because of the adverse effects of cigarette smoking on lung-function development. The objective of this paper is to systematically review the literature on the effects of active smoking on lung health in 12-25-year-old healthy boys and girls, measured with simple and noninvasive methods: lung function by spirometry, exhaled gases (including nitric oxide, carbon monoxide and hydrocarbons) and exhaled breath condensate. The identification of biomarkers may be useful for early detection of tobacco-related respiratory disease in this population, for targeted smoking prevention or smoking-cessation programs and, in the long term, for a reduction of personal and societal impact of COPD and other smoking-related diseases.