Lung cancer is mainly a lifestyle-associated disease with poor prognosis and the lowest five year survival rate of all types of cancer. Lung cancers are divided into two main groups: small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). Surgical treatment is generally indicated in cases of early stage NSCLC, and those patients treated with radical and aggressive surgery have a somewhat better survival rate. The main problems with lung cancer treatment are due to late diagnosis, rapidly developing drug resistance and side effects of the treatment that are experienced by almost all patients. The next step for distinguishing histologically complicated lung cancers and determining optimal treatment strategies is gene expression analysis. Supported by gene expression data, it is possible to prognosticate the course of the disease.