Using different homogeneous catalytic systems, the hydrocarboxylation of 1,2-polybutadiene (M(w) 2400) was achieved with partial to full conversion of pendant double bonds in a highly regioselective manner. The use of Pd(OAc)(2)/1,4-bis(diphenylphosphino)butane (dppb)/HCOOH or Pd(II)/dppb/ROH leads, respectively, to linear polyacids or polyesters. The extent of hydroesterification is controlled by the reaction time, temperature, and nature of the catalyst.