Abstract Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease, and infectious agents are suspected to be involved in the tumorigenesis of DLBCL. MicroRNAs (miRNAs) are non-coding RNAs modulating protein expression. We compared miRNA expression profiles in lymph node tissues of patients with DLBCL of the activated B-cell like (ABC) type from two geographical areas with different background exposures, Sweden and Egypt. We showed previously that DLBCL tissues of the ABC-type in Swedish patients had a higher expression of signal transducer and activator of transcription 3 (STAT3) compared to Egyptian patients. Here, we analyzed the involvement of miRNAs in STAT3 regulation. miR-1234 was significantly up-regulated in Egyptian patients with DLBCL compared to Swedish patients (p < 0.03). The miR-1234 expression level correlated inversely with the expression of STAT3. The Stat3 protein was down-regulated in cells transfected with miR-1234, suggesting that STAT3 might be a potential target for miR-1234. miR-1234 and STAT3 might be involved in the tumorigenesis of DLBCL of ABC type and possibly associated with environmental background exposure.