Horizontal and vertical advection of CO2 were measured at the Wetzstein site, a spruce ecosystem located on a hill near the village of Lehesten, Germany. These fluxes were measured during the CARBOEUROPE-IP advection experiment (ADVEX), carried out between April and June of 2006, when four additional towers were installed around the existing one, forming a polygon-like set-up [Feigenwinter et al. (2008)]. Measurements of wind speed, temperature, water vapour, and CO2 concentration were performed at 4 levels on all five towers. Horizontal gradients of CO2 were measured at 1.5 m in two perpendicular transects inside the area of the cube formed by the 4 towers. An additional tower was installed at one of the slopes of the hill. This tower was located at approximately 900 m from the hillcrest on the southwest sector, as this is the prevailing wind direction at the site. Horizontal and vertical advection terms were found to be related to cross-ridge flows, under specific micrometeorological conditions. Additionally, modelling results that support the existence of advection at low hills covered with a canopy were verified. According to these models, the flow passing over a low hill influences the wind velocity and scalar concentration fields above and below the vegetation, inducing advective transport of quantities such as CO2 [Finnigan and Belcher (2004); Katul et al. (2006)]. The first evidence was the reverse flow at the downwind side of the hill, obtained from the above and below-canopy measurements of wind direction at the tower located on the slope. The second experimental evidence came from the analysis of the horizontal gradient of CO2 inside the square formed by the ADVEX towers. According to this result, the CO2 accumulates close to the downwind side of the ridge, as confirmed by the modelling of the transport of scalars across a low hill covered with a canopy (Ned Patton, pers. comm.). The results presented in this work can be used to infer the existence of advective fluxes of CO2 in ecosystems located on similar topographies. The agreement of measurements with modelling work supports the theoretical approach about the influence of the flow passing over a low hill covered with a vegetation layer. These two sets of results help to expand the current knowledge of advection of CO2 over complex topographies.