The trace elements Hf-, Zr- and Ta-containing phases in the mother alloy, plasma rotating electrode processing (PREP) powders and hot isostatic pressed (HIPed) state of a new third generation nickel-based powder metallurgy (P/M) superalloy were studied. The results show that the trace elements Hf, Zr and Ta mainly exist as MC-type carbides which locate between the dendrites and in the shape of block, strip and butterfly. The carbides in PREP powders can be broadly divided into two groups. One is rich in Ti, Ta and Nb, and the other contains the elements of Ta, Hf and Zr. The two types of carbides both contain a certain amount of non-carbide forming elements Co and Ni, weak carbide forming elements Cr and Mo, and locate between the dendrites or cellulars and in the shape of block and granular. In addition, the analysis of HIPed alloy show that the trace elements Hf, Ta and Zr mainly exist as intragranular and grain boundary MC carbides. All of these indicate that the trace elements Hf, Zr and Ta are in the survival of MC-type carbides and with the genetic characteristic. Carbides and γ' phase of HIPed alloy contain less Ta compared with PREP powders.