In this paper, we propose to study the influence of moisture on passive radiofrequency (RF) sensors associated with poly (3,4-ethylenedioxythiophene) polystyrene sulfonate - multi walled carbon nanotubes (PEDOT:PSS-MWCNT) as a sensitive material. The designed sensor consists of a copper ring resonator and two PEDOT:PSS-MWCNT stubs located in the maximum electric fields of the fundamental resonant mode operating at 3.94 GHz. For performing a differential analysis, experiments are conducted by considering the resonant structure with and without a sensitive layer. Our experiments show the high interference of humidity on the sensor’s performances and highlight the importance of differential study to decorrelate physical and chemical surrounding parameters. This differential innovative structure paves the way for a very high sensitive passive RF sensor dedicated for gas sensing.