microRNAs (miRNAs) are a highly conserved class of small noncoding RNAs that regulate gene expression by post-transcriptional degradation or translational repression. miRNAs are involved in the regulation of cell apoptosis, proliferation, differentiation and other physiological processes, and are closely related with the development of cancer. More recently, it has been proposed that the presence of genetic variations (e.g., single nucleotide polymorphism and copy number variation) in microRNA genes, their biogenesis pathway and target binding sites affect the miRNA processing machinery and targeting, and have a significant genetic effect. In this review, we focus on the miRNA-related genetic variations and cancer susceptibility and progression.