Lung cancer is the leading cause of cancer-related mortality worldwide. All drugs available for the treatment of lung cancer reached the market after reporting positive results from pivotal clinical studies. However, in these trials not all patient subgroups are adequately represented, with some discrepancies reported in patients' accrual especially concerning age, gender and ethnicity. Hence, a new drug entering the market for the treatment of all patients may have been investigated only in certain patient subgroups, while the reported results have been generalized for the therapy of all patients. The impact of certain characteristics such as gender, ethnicity and age of patients enrolled in randomized trials on the final results has been examined and discussed in this article.