A time series analyses of planetary boundary layer ozone data is presented from 1990 to 2001. The ozone data is obtained from the Uccle (50o48’N, 4o 21’E) balloon sound-ing time series. This planetary boundary layer ozone is an averaged concentration within this layer, which is more representative on a regional scale. The climatology of the 1990-2001 time series has two ozone maxima: a maximum during spring and a maximum during the summer. To better elucidate this dependence from ozone on meteorology, 5 multiple linear regression models have been designed (four models for each climatological season and one overall model), using different meteorological parameters. For choosing the best models, a stepwise selection has been applied, using Cp-statistics. The composite model exhibits a significant larger R2 and a smaller rmse when compared to the overall model. During the spring season, the mixing altitude is the most important contributing parameter while during the summer season, temperature and radiation are the most important contributing parameters, suggesting that different meteorological regimes are the cause for the spring and the summer ozone maxima