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In this work, we report on the anomalous conductance induced by hydrogen (H2) gas on as-grown and gold/palladium (Au/Pd)-catalyzed zinc oxide nanoflowers (ZnO NFs). The catalyzed ZnO NFs exhibited a sharp increase in conductivity on H2 exposure and the conductance persisted for several hours on removing H2. This anomalous behavior is in sharp contrast to conventional ZnO-based H2 gas sensors wherein the conductivity decreases on removing H2 gas. The as-grown ZnO NF sample showed drastic response to H2 under UV illumination with its conductivity increasing by almost 500%. We attribute our observation to catalyzed chemidesorption of oxygen from the ZnO lattice. [ABSTRACT FROM AUTHOR]