Hodgkin's lymphoma (HL) is a B cell‐derived lymphoma characterized by a minority of malignant Hodgkin Reed–Sternberg (HRS) cells that have lost their normal B cell phenotype. Alterations in the cell cycle and apoptosis pathways might contribute to their resistance to apoptosis and sustained cell cycle progression. A key player in both cell cycle arrest and apoptosis is CDKN1A, encoding p21 ^waf/cip1 (p21). P21 is regulated by p53 and can function as a cell cycle inhibitor when in the nucleus or as an apoptosis inhibitor when localized in the cytoplasm. We observed expression of p53, p21 and p‐p21 in a variable number of HRS cells in 24 of 40 cases. Expression of miR‐17 and miR‐106a was detected in HRS cells of 10 HL cases. MiR‐17/106b seed family members, CDKN1A RNA and p21 protein levels were variable in HL cell lines. We showed effective targeting of the CDKN1A 3′ UTR by miR‐17/106b in HL cell lines in a luciferase reporter assay and up‐regulation of p21 protein levels upon anti‐miR‐17 treatment of KM‐H2 cells. Functional studies indicated a p21‐mediated G1 arrest after miR‐17/106b down‐regulation in KM‐H2, whereas no G1 arrest was observed for U‐HO1 and L428. This difference could not be explained by differences in the 3′ UTR, the cellular location of p21 or expression variation during cell cycle progression. A strong correlation was observed for the miR‐17/106b: CDKN1A ratio and the responsiveness to miR‐17 inhibition, ie a low ratio in KM‐H2 and an extremely high ratio in the two unresponsive HL cell lines. In conclusion, we show that miR‐17/106b regulates p21 protein levels in HL and that the effect of miR‐17/106b‐mediated inhibition depends on the miRNA: target gene ratio. Thus, in HL high miR‐17/106b expression contributes to a dysfunctional p53 pathway and thereby also to the malignant phenotype. Copyright© 2011 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.