There is a demand to understand B-cell lymphoma pathogenesis better, to identify new markers, and to define multiple lymphoproliferative disorders more accurately. MicroRNAs (miRNAs) are regulators of protein translation, comprising a group of more than 1500 short noncoding single-strand RNA molecules of approximately 22 nucleotides in length. They are easily detectable in fresh or paraffin-embedded diagnostic tissue and serum. Expression of individual miRNAs and miRNA signatures allows specific cell-differentiation stages to be identified, and is a powerful diagnostic and prognostic method. Here we review what is known about the pathogenic relevance of miRNAs, and use of miRNAs for the diagnosis and prognosis of B-cell lymphomas. Most of the published data concern chronic lymphocytic lymphoma and diffuse large B-cell lymphoma, and implicate miRNAs in the pathogenesis of these diseases. They identify miRNAs that could be used for diagnosis, prognosis, or prediction of response to specific therapies.