Every summer, ozone smog episodes systematically take place in large agglomerations. In order to prevent them, a better understanding of formation dynamics is needed using numerical models. These models must, however, be validated. Lidar is a unique tool for this task since it provides 3D measurements, for example combining 2D spatial measurements with time in an "animation movie". We present here two recent examples of such ozone Lidar measurement campaigns: the first over Lyon, was mainly used to evaluate a UAM-V type photochemical model and obtain ozone inter comparison data between ground level monitors and Lidar results. The other was performed in Paris and dedicated to validating the Lidar measurements themselves
