A smart porous conductive polymer composite (CPC) consisting of cellulose acetate as matrix and multiwalled carbon nanotubes as conductive filler was prepared to detect a set of lung cancer biomarkers. The solvent evaporation-induced phase separation was used to introduce porosity into the conductive composite. The prepared sensitive layers exhibited high response intensity, low response time, and good recovery behavior toward the mentioned analytes. A thorough investigation was conducted on the morphology, response behavior, sensitivity, and selectivity of the prepared CPC transducer. The selectivity of responses was considered based on the thermodynamic and kinetic characteristics of polymer and analytes such as Hansen solubility parameters, Flory-Huggins interaction parameter, and diffusion coefficient of analytes into the polymer membrane. Moreover, the microstructure of porous layers was characterized by using SEM, contact angle, and BET. The volume porosity and specific surface area of the sensitive layers were increased by the introduction of porosity into the polymer composite, causing the improvement of sensing parameters. The obtained responses further confirmed the promising potential of the prepared porous CPC structure, for the detection of lung cancer biomarkers, from exhaled breath as an inexpensive, repeatable, accurate, and noninvasive method.