Effects of a polydisperse cloud on tropospheric chemistry have been studied in the framework of a two-dimensional model where dynamical, microphysical, and chemical processes are fully interactive. The chemical module describes the tropospheric photochemistry of ozone precursors in both gaseous and aqueous phases for a remote atmosphere. Impacts of the cloud polydisperse feature have been obtained by comparing the results in the case of a mono-disperse cloud created under the same meteorological conditions. The /2> ratio decreases more sharply in the case of the polydisperse cloud. The partitioning of the most soluble species does not follow the Henry's law equilibrium except in the middle of the cloud. This result has implications for airborne measurements made within clouds. Deviations from Henry's law found in samples are usually explained only by the effect of variations of the liquid water content with time, assuming that no real deviations exist in the real cloud. Here, it is shown that deviations from Henry's law equilibrium may exist even for clouds consisting of small droplets. ¿ American Geophysical Union 1996