The Roque de los Muchachos Observatory, located on the island of La Palma in the Canary Islands, is home of many astronomical facilities. In the context of the Extremely Large Telescope Design Study, an intensive lidar campaign was performed in the ORM near the Jacobus Kapteyn Telescope (17°52'41.2" W, 28°45'40.1" N, 2395 m asl) between 26th May and 14th June 2008. The goal of the campaign was to characterize the atmosphere in terms of planetary boundary layer height and aerosol stratification vs. synoptic conditions. As a by-product an estimate of the aerosol optical thickness was also obtained and compared to the total atmospheric extinction coefficient measured by the Carlsberg Meridian Telescope.