, 0.01, 0.03, 0.05 and 0.1 was studied in the frequency range of 10 kHz-1 MHz over the temperature range of 300-850 K. It is found that the chemical substitution of Cd ions at the Ca sites results in decrease in dielectric constant by 9% -55% for Cd-doped CaCu 3 Ti 4 O 12 , at room temperature. Although the decrease in the dielectric constant was observed by Cd doping, no drastic suppression of dielectric response could be observed by Cd-doping. The dielectric anomaly was found at T 1 (727 K for x=0.05), which suggests a phase transition. This T 1 decreases linearly with increasing x. CdCu 3 Ti 4 O 12 is still a member of high-dielectric materials.