Lung cancer is one of the leading causes of cancer-related death in the world. Developing minimally invasive techniques that can detect lung cancer, particularly at an early stage, as well as predict metastasis and prognosis, is an important strategy to improve the outcome. MicroRNA (miRNA) are a class of small non-coding RNA species that play important roles in tumorigenesis and tumor development by binding to their target mRNAs and inducing translation inhibition and/or mRNA degradation. Dysregulation of miRNAs is frequently found in malignancies, including lung cancer. Recent studies have revealed that miRNA are not only stable in paraffin-embedded tissues and body fluids, but also in plasma and serum, which makes circulating miRNA a new kind of ideal biomarker that opens a new field for early molecular diagnosis of lung cancer, as well as for prediction of lung cancer metastasis and survival.