A kinetic study on CH 4 combustion over a PdO/ZrO 2 (10%, w/w) catalyst has been performed in a temperature range between 400 and 550 o C by means of an annular catalytic microreactor.The role of mass transfer phenomena including diffusion in the catalyst pore, gas-solid diffusion and axial diffusion in the gas phase, has been preliminary addressed by means of mathematical modeling. Simulation results have pointed out the key role of internal diffusion showing that thicknesses of the active catalyst layer as thin as 10-15μm are required to minimize the impact of mass transfer limitations. The thermal behavior of the reactor has been also addressed by means of catalytic combustion tests with CH 4 and CO-H 2 mixtures as fuels. The results have demonstrated the possibility to obtain nearly isothermal temperature profiles under severe conditions (up to 3% of CH 4 ) thanks to effective dissipation of reaction heat by radiation from the catalyst outer skin.Finally the effect of reactants (CH 4 and O 2 ) and products (H 2 O and CO 2 ) on CH 4 combustion rate has been addressed. The results have shown that both H 2 O and CO 2 markedly inhibit the reaction up to 550 o C. The data have been fitted by the following simple power law expression r=k r P C H 4 P H 2 O - 0 . 3 2 P C O 2 - 0 . 2 5 with an apparent activation energy of 108kJ/mol.Evidences have been found and discussed indicating a key role of the support on the extent of such inhibition effects.