Liver cancer (hepatocellular carcinoma, HCC) is a major malignancy worldwide. Etiologically, hepatocarcinogenesis is closely associated with HBV and HCV infections; however, its underlying molecular mechanism is not completely understood. MicroRNAs are a class of small non-coding RNAs that negatively regulate gene expression by interacting with the 3'UTR of protein-coding mRNA. MicroRNAs are implicated in nearly all major biological and cellular events, and recent findings further link microRNA deregulation to human carcinogenesis. In this review, we will focus on the aberrant expression of miRNAs in liver cancer and the pathological implications and molecular functions of some well-characterized oncogenic and tumor suppressive miRNAs. Finally, the clinical prospect of miRNAs as a novel diagnostic and therapeutic intervention will be discussed.