Accurate high-pressure thermal conductivity measurements have been performed on H2O + CdCl2 and H2O + CdBr2 mixtures at pressures up to 100 MPa in the temperature range 293-413 K by use of a parallel-plate apparatus. The concentrations studied were 0.025, 0.05, 0.10, 0.15, 0.20, and 0.25 mass fraction of salts. The estimated accuracy of the method is about +/-1.6%. The pressure, temperature, and concentration dependence of the thermal conductivity has been studied. Measurements were made on six isobars, namely : 0.1, 20, 40, 60, 80, and 100 MPa. The thermal conductivity shows a linear dependence on pressure and concentration at all isotherms. Along each isobar, a given concentration shows the thermal-conductivity maximum at temperatures of about 413 K. The measured values of thermal conductivity at atmospheric pressure are compared with the results of other investigators. Literature data at atmospheric pressure reported by Eldarov and Zaitzev agree well with our thermal conductivity within our estimated accuracy.