Prognostic factors play a critical role in explaining the outcome of patients with lung cancer. They are vital in clinical tasks such as individual advising, choosing among different treatment options, and stratifying for groups of comparable risks. They also are vital in designing new studies, interpreting the literature, and understanding the biologic nature of the disease. Traditionally, it is assumed that the anatomic extent of disease, the patient's performance status, and a few other anthropometric variables are all that is needed for a reliable prognostic assessment. In the advanced stages of non-small cell lung cancer, the use of simple biochemical tests is considered an additional valuable option. For years, serum tumor markers have been used to monitor the clinical course of lung cancer, and their prognostic capability appears certain. The prognostic factor quality of life is already supported by clear and indubitable evidence. Recently, newer biologic prognostic determinants have captured the attention of researchers. Intriguing patient-related factors such as the mental state of depression might be recognized as important in the future. Although the life span of an individual patient may never be calculated mathematically, its approximation becomes increasingly satisfactory as new prognostic factors are explored.