Adenocarcinoma of the lung is now the most frequent histological subtype of lung cancer in North America. The increase in cases of adenocarcinoma of the lung has begun since the seventies and has been attributed to the changes in smoking habits and to the rise of lung cancer incidence in females who preferentially develop adenocarcinoma. In France, squamous cell carcinoma of the lung still predominates, but a recent increase in adenocarcinoma has been observed. We performed a comparative study of the smoking habits of patients referred to the chest diseases or to the thoracic surgery departments of the University Hospital of Strasbourg for either a squamous cell carcinoma or an adenocarcinoma, between march 1st, 1995 and april 30th, 1998. The statistical analysis, based on conditional logistic regression, was performed after matching one adenocarcinoma with one squamous cell carcinoma. The matching factors were age, gender and the date of diagnosis. Patients with adenocarcinoma were significantly younger when they started smoking and when they quitted smoking. In these patients, there was also a trend towards a more frequent deep inhalation and use of filter cigarettes. On the other hand, patients with a squamous cell carcinoma smoked more frequently hand-rolled cigarettes. There was no difference with respect to environmental tobacco smoke exposure.