High-quality ZnSe single-crystals were grown on a ZnSe(1 1 1)B seed by vertical sublimation method. The seeds were 0.7 mm thick and 9.7 mm in diameter. We found that annealing for 10 h before growth caused the seeds to become spherical and their diameter decreased to 5 mm, without any decrease in volume. In addition, the crystallographic quality of the grown crystals strongly depended on the seed annealing time. Crystal characterization was carried out using high-resolution X-ray diffraction (HRXRD) and X-ray topography (XRT). When the annealing time was 1 h, the full-width at half-maximum (FWHM) of the X-ray rocking curve (XRC) was wider than 40 arcsec and the XRT intensity was not uniform. In contrast, when the annealing time exceeded 5 h, the FWHM of the XRC was narrower than 10 arcsec and the XRT intensity was uniform. The optimal FWHM of XRC was 6.7 arcsec and occurred when the annealing time was 10 h.