Adsorption of NO on Co-ZSM-5 results in formation of three kinds of Co3+-NO species (1970, 1957 and 1940 cm(-1)) and Co2+ (NO)(2) dinitrosyls (1894 and 1811 cm(-1)). All these species disappear after evacuation at elevated temperatures. However, a very short evacuation of the sample with preadsorbed NO at 673 K, followed by quenching to room temperature, results in appearance of a band at 1857 cm(-1). This band is assigned to Co2+-NO linear species produced after partial destruction of the dinitrosyls. The reasons for the different pathways of the dinitrosyl decomposition are discussed. (C) 2003 Elsevier Science B.V. All rights reserved.