In order to study the behaviour of stratospheric minor constituents related to aeronomic processes and atmospheric transport in the meridional plane, a numerical two-dimensional model is established. The stratospheric dynamics is parametrized by mean motions and large scale eddy diffusion. This model is applied to the study of ozone in a nitrogen-hydrogen-oxygen atmosphere. The analysis of the various results indicates that the distribution of O3 is related to the existence of a countergradient flux which is responsible for the transfer of these molecules from the equatorial regions where they are produced to the polar regions where they accumulate during the winter season. The model also shows the combined action of nitrogen and hydrogen compounds on the ozone layer. The particular role of nitric acid on the stability of stratospheric ozone is discussed.