MicroRNAs (miRNAs) are a class of short regulatory non-coding RNAs (22-24 nt) widely expressed in living organisms. Shortly after their discovery, microRNAs are found to participate in the development of a variety of diseases. miR-17-92 and its paralog are one of them, recent studies have revealed their critical roles not only in the development of lung, heart, immune system but also in carcinogenesis. The present article mainly focuses on their different expression patterns and molecular mechanisms to elucidate their contribution to cancer development.