The present paper tested one of the hypotheses on the inability of regional air quality models in capturing dynamic range of diurnal ozone variations in the cells away from urban or large NOx emissions sources. It focused on the model bias caused by the limited vertical resolution of the emissions layer. The tests with a simple box model and a modified version of limited domain Regional Acid Deposition Model (WRADM) suggest that predictions of nighttime ozone minimum concentrations by the regional models can be improved by introducing vertical layers that limit excessive vertical dilution of surface emissions from area and mobile NOx emissions. The increased vertical resolution not only helps the depiction of emissions distribution, but also provides a more realistic set of meteorological input parameter values to the model, which in turn improves the model predictions of daily minimum ozone concentrations.