Affibody molecules (AffB) are small (~ 6 kDa) and robust non-immunoglobulin affinity ligands capable of binding to a wide range of protein targets. Because of many advantages, they can be used as tools for molecular recognition in diagnostic and therapeutic applications. The human epidermal growth factor receptor 2 (HER2) (ErbB2/neu) receptor tyrosine kinase is often overexpressed in several different carcinomas, and it has attracted attention for use as a tumour marker in bioimaging and drug delivery systems. Therefore, binding molecules with the ability to target Her2 have been developed, for instance ZHER₂:₂₈₉₁, which comprises a cysteine residue (C-terminus). Three affibody conjugates (monoaffibody AffB-1MI and two diaffibodies AffB₂-2MI and AffB₂-3MI) were obtained by covalent coupling with bispecific linkers based on flexible PEG chains (maleimide-thiol conjugation), combined with a fluorescent pattern. Flow cytometry was performed to show the cell binding ability of the affibody conjugates to HER2-overexpressing cell line, SKOV3 cells, and HER2 low-expressing cell line, HeLa cells. It was found that all three conjugates could bind specifically to Her2, but AffB-1MI could bind more effectively to HER2-expressing cells. This study also showed that only anti-proliferative effect of AffB-1MI has some significance. Since AffB-1MI shows best results, it could be also used for imaging purposes. Optimization of all three conjugates might be further considered for developing tumour-targeting applications and for diagnostics and immunotherapy of adenocarcinomas such as breast and ovarian cancers.