Applicants describe the synthesis of fluorotamoxifen and iodotamoxifen analogs with the halogen atom positioned on the aliphatic chain of the tamoxifen molecule. The halogenated-tamoxifen derivatives possess superior binding affinities to estrogen receptors of pig uteri compared with tamoxifen. The fluorinated tamoxifens have potential use in imaging estrogen receptors by PET whereas the iodinated tamoxifens have potential use in imaging estrogen receptors by SPECT. Rapid and efficient methods of preparing fluorotamoxifen and iodotamoxifen derivatives with high specific activity are also disclosed. Fluorotamoxifen and iodotamoxifen derivatives may advantageously be used as anti-cancer therapeutic agents to halt estrogen-receptor positive tumors.