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The aim of this work is the development of vapor detectors formed from composites of conductive carbon black and insulating organic multifunctional polymers having metal ions complexing ability. The new materials are tailored to produce increased sensitivity toward specific classes of analyte vapors. For comparison purpose, poly(vinyl chloride) (PVC) with di(2-ethylhexyl)phthalate (DOP), a traditional low molecular weight plasticizer, is used as representative of the behavior of a traditional composite vapor detector. Resonant frequency shift of a quartz crystal microbalance (QCM) and dc resistance measurements have been performed simultaneously on polymer–carbon black composite materials. The proposed materials showed an enhanced sensitivity upon exposure to acetic acid and amines vapors; the performances of our systems are 103 times higher than those of a traditional composite vapor detector. Moreover the extent of such responses is beyond that expected by mass uptake upon exposure to the same vapors and cannot be attributed solely to differences in polymer/gas partition coefficients. In this respect, several different chemical factors determine the dc electrical response of this system: in our opinion changes in polymer conformation during the adsorption process also play a significant role.