Phase relations in Cu-Ti-Hf ternary system have been studied by diffusion triple technique supplemented with typical alloy sampling method. Based on results from electron-probe microscopy analysis and X-ray diffraction, isothermal sections of the Cu-Ti-Hf system at 800 and 700 A degrees C were established, which consist of ten and nine three-phase regions, respectively. It is observed that Ti can completely substitute Hf in the CuHf2 phase, indicating formation of a continuous solid solution Cu(Ti,Hf)(2). Hf can substitute about 20% Ti in the phase CuTi, while solubility of Ti in Cu10Hf7 and Cu51Hf14 phases reaches to 14 and 11 at.% at 800 A degrees C, respectively. The Cu8Hf3 phase in existence at 800 A degrees C was proved to be unstable at 700 A degrees C. In addition, the elastic modulus and hardness of solid solution Cu(Ti,Hf)(2) were determined by using nano-indentation techniques.