Lung cancer is the leading cause of cancer-related deaths in the US and worldwide. Better understanding of the disease is warranted for improvement in clinical management. Here we summarize the functions of small-RNA-based, posttranscriptional gene regulators, i.e. microRNAs, in the pathogenesis of lung cancers. We discuss the microRNAs that play oncogenic as well as tumor suppressive roles. We also touch on the value of microRNAs as markers for diagnosis, prognosis and the promising field of microRNA-based novel therapies for lung cancers.