Low-rate smoking patterns are common, but their pulmonary effects remain poorly known. The study hypothesis was that any level of daily smoking may cause chronic obstructive pulmonary disease (COPD). We investigated the association between longitudinal smoking patterns and COPD using logistic regressions and survival models adjusted for multiple covariates. Data from Finnish Twin Cohort surveys were used. Participants (n = 21,609) were grouped into categories describing 1981 smoking and change in smoking during 1975-1981. Light smoking was defined as < 5 cigarettes per day, moderate 5-19 cigarettes, and heavy ≥ 20 cigarettes per day. Finland's Social Insurance Institution provided data on inhaled anticholinergics purchases (1995-2008) and diagnoses entitling to special reimbursements (1981-2008). We defined COPD as regular anticholinergic use or special reimbursement eligibility for COPD, emphysema, or chronic bronchitis. COPD incidence was 2.5% (n = 528). Elevated disease risks were observed in former, moderate, and heavy smokers, in all who increased smoking, and in those who reduced from moderate to light smoking. Increased risk for anticholinergic use was found in former smokers, in constant light, moderate, and heavy smokers, and in increasers. Former, light, moderate, and heavy smoking in 1981 was associated with future development of disease. Our results demonstrate that all daily smoking patterns may impair pulmonary function.