Chemical reactions in a dielectric barrier discharge at medium pressure of 250-300 mbar have been studied in CH4/Ar and CH4/N-2 gas mixtures by means of mass spectrometry. The main reaction scheme is production of H-2 by fragmentation of CH4, but also production of higher order hydrocarbon molecules such as CnHm, with n up to 9 including formation of different functional CN groups is observed. Formation of C2H2, C2H4, and C2H6 molecules has been investigated in some detail. Significant differences are noted in comparison to a theoretical estimate.