A heterogeneous group of cancers of pulmonary originKnown risk factors: first and foremost smoking; in addition work-related exposure agents in certain occupations Particular groups at risk include middle-aged and older (over 45 years) smokers with e.g. altered characteristics of usual cough, haemoptysis recurrent respiratory infections weight loss and impaired general condition. Some lung cancers, however, develop in non-smokers or people who have smoked only a little.