Synthesis, structural characterization and biological activity against several human tumor cell lines of four rhenium(I) diseleno-ethers complexes: Re(CO)3Cl(PhSe(CH2)2SePh), Re(CO)3Cl(PhSe(CH2)3SePh), Re(CO)3Cl(HO2C-CH2Se(CH2)2SeCH2-CO2H) and Re(CO)3Cl(H

► Four rhenium(I) diseleno-ethers complexes were prepared. ► Structure were established by spectroscopic methods and X-ray diffraction analysis. ► Antiproliferative activity of these complexes was determined.