Langmuir-Hinshelwood and power equations were used for the description of a chemical reaction on a pore wall in the transition kinetic region, where the reaction rate is determined both by diffusion into the pore and by the chemical reaction at the interface. The exponent in the power equation corresponding to the chosen constants in the Langmuir-Hinshelwood equation was calculated by the least squares method. The concentration distribution in the pore and the effectiveness factor as function of the dimensionless modulus h is an element of (0, 4) were calculated for both kinetic equations. The deviations of the effectiveness factor found for the corresponding power equation with respect to the Langmuir-Hinshelwood equation were smaller than +/-5% for a porous catalyst in the form of an infinite plate or a sphere, assuming that the true reaction order was 1 or 2 and that the exponent in the power equation was higher than 0.125.