The NO2 gas-sensing characteristics of chemiresistors in the form of multilayered Langmuir-Blodgett films of a symmetrically substituted phthalocyanine, containing on the periphery four amidic groups -CONH-, have been studied. Floating layers were spread onto the water surface from a chloroform solution and were transferred onto both hydrophilic and hydrophobic quartz substrates using the vertical lifting method. Response and recovery times have been measured for different working temperatures at a fixed NO2 concentration. Dynamic response characteristics of the electrical conductance of the LB films to different NO2 concentrations, carried out in dry air, have shown a high sensitivity to concentrations of nitrogen dioxide smaller than 20 ppm at room temperature. All measurements have been carried out using coplanar configurations of the devices.