Emission characteristics of the filtration combustion waves freely propagating in an inert packed bed are studied experimentally. The waves were formed under filtration of lean and ultra-lean methane/air mixtures with equivalence ratios from 0.25 to 0.9 and filtration velocities from 10 to 40 cm/s. Downstream (superadiabatic) and upstream (underadiabatic) propagation of filtration combustion waves was observed depending from experimental conditions. Stabilized by intensive heat transfer in the traveling wave, the combustion temperature shows only small variation (100 to 200 K) over the range of the equivalence ratios studied. The NOx and CO emissions are found to be very low throughout ultra-lean region (φ <0.5). In this area, NOx levels are lower than 4 ppm and CO levels are below 10 ppm. The NOx concentration grows with equivalence ratio, while faster filtration velocities correspond to higher NOx levels. Measured CO emissions are only slightly influenced by experimental conditions at the equivalence ratios below 0.8. More complex behavior is observed for φ > 0.8. In this region the experimental data shows rapid increase in CO concentrations after critical equivalence ratio, which is found to be lower for high filtration velocities.