The glass-forming region in the pseudo-ternary CdSe–AgI–As2Se3 system was determined. Measurements including differential scanning calorimetry (DSC), density, and X-ray diffraction were performed. The effect resulting from the addition of CdSe or AgI has been highlighted by examining three series of different base glasses. The characteristic temperatures of the glass samples, including glass transition (Tg), crystallisation (Tx), and melting (Tm) temperatures are reported and used to calculate their ΔT = Tx − Tg and their Hruby, Hr = (Tx − Tg)/(Tm − Tx), criteria. Evolution of the total electrical conductivity σ and the room temperature conductivity σ298 was also studied. The terahertz transparency domain in the 50–600 cm−1 region was pointed for different chalcogenide glasses (ChGs) and the potential of the THz spectroscopy was suggested to obtain structural information on ChGs.Graphical abstractResearch highlights▶ Determination of the glass-forming region in the pseudo-ternary CdSe–AgI–As2Se3 system. ▶ Characterization of macroscopic properties of the new CdSe–AgI–As2Se3 glasses. ▶ Far infrared transmission of chalcogenide glasses. ▶ Characterization of the total conductivity of CdSe–AgI–As2Se3 glasses.