The invention relates to microRNA-34a and related microRNAs for use in the treatment of B-cell lymphoma. Likewise it relates to microRNA-34a for use in the preparation of a medicament for the treatment of B-cell lymphoma, and for a method of treatment of B-cell lymphoma comprising administering microRNA-34a. These claims are based on the observation that microRNA-34a shows strong anti-proliferative effects when overexpressed in diffuse large B-cell lymphoma (gDLBCL) cell lines, or when delivered intratumorally or systemically in xenograft models of DLBCL.