The low-temperature adsorption and co-adsorption of CO and 15N2 on a series of Me-EMT zeolites (Me=Li, Na, K, Rb and Cs) have been studied by FTIR spectroscopy. Adsorption of 15N2 on Na-EMT at 85 K results in the formation of Na+ (15N2)2 geminal species (IR band at 2255 cm-1), which are converted, at low equilibrium pressures, into Na+–15N2 linear complexes (IR band at 2258.5 cm-1). Both species are removed by evacuation. CO adsorption at 85 K results in the formation of dicarbonyls at high pressures (2164 cm-1), which are converted into linear carbonyls at low pressures (2175 cm-1). Mixed Na+(15N2)(CO) complexes are produced when 15N2 and CO are co-adsorbed. The latter easily lose one 15N2 ligand, thus being converted into linear carbonyls. On Li-EMT only Li+–15N2 species were detected, characterized by a band at 2263 cm-1, and only linear Li+ carbonyls were produced after CO adsorption (band at 2183 cm-1). In addition, a weak band at 2199 cm-1 (tentatively assigned to the Al3+–CO species) was detected. The spectra of 15N2 and CO adsorbed on K-EMT, Rb-EMT and Cs-EMT display some similarities. In all cases geminal and linear dinitrogen complexes are detected; however, the spectral differences between them are very small. Upon CO adsorption two principal bands (2160 and 2147 cm-1 for K-EMT; 2159 and 2151 cm-1 for Rb-EMT; and 2157 and 2144 cm-1 for Cs-EMT) and two weak features (2275 and 2120 cm-1 for K-EMT; 2261 and 2119 cm-1 for Rb-EMT; and 2242 and 2123 cm-1 for Cs-EMT) are detected. Analysis of the spectra allows assignment of the bands around 2120 cm-1 to O-bonded CO, the bands in the 2185–2155 cm-1 region to CO polarized by metal cations, and the band at 2151–2144 cm-1 to mixed Me+(OC)(CO) species. The reasons for the formation of different complexes are discussed.