Polymer/conductive nanoparticle composites are being created and tested for different sensor applications by many scientific groups. Our work was done to be able to better optimize polyisoprene/nanostructured carbon black (PNCB) composites for sensor application by carrying out relative conductance change (RCC) measurements in alternating current mode while inducing mechanical deformation in the composites. PNCB samples with different amount of nanostructured carbon black filler were tested in the frequency range from 20 Hz to 2 MHz. The measurements showed that maximum RCC for PNCB samples with low carbon black filler concentration (4-5 mass parts of carbon black per 100 mass parts of polyisoprene) is found only at the lowest measured frequencies, but PNCB samples with high filler concentration (8-10 mass parts of the filler) showed a wide, constant RCC plateau up to at least 10 kHz.