Lung cancer is nowadays the most spread cancer worldwide, being the main cause of death of all cancers. Lung cancer is the most important and frequent type of lung tumour, representing over 90% of all cases of primary malignant and benign lung tumours. The most deaths of lung cancer occur at 35-75 age group. In the eighties, lung cancer was estimated to be almost 16% of all cancers worldwide and almost 23% of all cancers in Europe. In 1999, lung cancer relative frequency in USA was on top, being followed by colonic cancer and breast cancer relative frequency. In the same year, relative frequency of lung cancer was higher in USA than in Romania both for men (33.97% to 28.4%) and for women (about three times higher in USA than in Romania). According to statistics, lung cancer mortality rate in Romania in 1999 was on the first place in men (comparative with mortality rate of other cancers) and on the third place in women (after breast cancer and uterine collum cancer mortality rate). Lung cancer mortality rate in Romania increased significantly in 1985-2003 period, from 24.9%000 in 1985, to 39.7%000 in 2003. In 2000 year, lung cancer incidence for men in Romania (67.1%000) was lower than in Yugoslavia, Croatia, Bosnia-Herzegovina and Bulgaria but higher than its corresponding value in Macedonia and Albania. Prospective statistic studies estimate that in 2020 year lung cancer incidence for men will be the highest in Greece, Spain and France and the lowest in Great Britain, Ireland, Finland and Sweden. For women, the highest lung cancer incidence is estimated to be in Holland, Denmark and Austria and the lowest in Spain, Ireland and Finland.