A prospective computed tomographic (CT) study was performed to determine the prevalence of lung changes in smokers. The study group comprised 175 healthy adult volunteers (current smokers, n = 98; ex-smokers, n = 26; nonsmokers, n = 51). The subjects underwent clinical examination, pulmonary function tests, chest radiography, and conventional and high-resolution CT (HRCT). Significant differences between current smokers, ex-smokers, and nonsmokers were observed with HRCT in the identification of subpleural (P = .11) and parenchymal (P < .001) micronodules, emphysema (P < .001), and areas of ground-glass attenuation (P = .0001). All subjects had normal pulmonary function. Parenchymal micronodules, areas of ground-glass attenuation, and emphysema were observed with a significant predominance in the upper lung zones (P < .01). Presence of emphysema and abnormal bronchial wall thickening were the only HRCT signs associated with significantly lower values of functional parameters. These data support the concept that parenchymal abnormalities can be detected in healthy smokers with normal findings at chest radiography and pulmonary function tests.