The aim of this work is to research the influence of the arrangement of conductive filler channel microstructure on the piezoresistive effect of the polyisoprene – highly structured carbon black (PiCB) composite. PiCB samples ranging from 6 to 10 phr of CB (5 parallel samples) were prepared and investigated. Each sample was measured with electro-conductive mode of atomic force microscopy (EC-AFM) to obtain a map of the electro-conducting channels formed from CB particles. Mathematically processing the data, we obtain indexes, which characterize channel distribution and channel size distribution. The sample piezoresistive effect was determined with the universal testing machine Zwick, in compression mode to 105 Pa. Samples with 6 and 7 phr of CB show positive piezoresistive effect – the electrical resistance increases with increasing pressure, on the other hand samples with 8-10 phr of CB show an opposite – negative piezoresistive effect – the electrical resistance decreases with increased pressure. A correlation between the filler formed microstructure and the piezoresistive effect is analyzed.