This work reports the results of experimental and theoretical investigations of NO decomposition in a catalytic monolith reactor. Monolithic catalysts are composed of a commercial cordierite substrate (Corning Inc.) and copper containing ZSM-5 zeolite (Si/Al = 40; 1.92% Cu). Laboratory scale activity tests were carried out in the integral monolith reactor, operating under atmospheric pressure at different temperatures (573-773 K) and at various space times. The reactor performance was modeled using several mathematical models. The kinetics of NO decomposition was described by a LHHW type rate equation. The parameters of the monolith reactor models were estimated from experimental data using a modified differential method and Nelder-Mead method of non-linear optimization. It was found that the behavior of the experimental monolithic reactor was mainly limited by interphase mass transfer. The 2D heterogeneous model with distributed parameters was determined to be the most suitable mathematical model for detailed consideration of physico-chemical processes occurring in the catalytic monolith reactor.