We have used specular neutron reflectivity to study adsorbed layers of a modified polysaccharide bearing lateral cholesterol anchors (cholesterylpullulan, CHP) at the air-water interface. In this system, the otherwise non surface active polysaccharide is attached, at several points along the backbone, to the surface by the hydrophobic cholesterol groups. The properties of these adsorbed polymer layers have been studied for different degrees of cholesterol substitution varying from 0.6 to 1.4 mol % and for different bulk concentrations. Using a parabolic profile to describe the adsorbed layer, it is found that the thickness of the layer decreases with surface concentration. These results are in contrast to those reported for end-attached tethered polymer layers. We attribute this behavior to the associative properties of the polymer as the interacting cholesterol groups are increased in the layer. Furthermore, the amount of polymer adsorbed decreases with the degree of cholesterol substitution. Surface tension data show that very long equilibration times are required for the formation of the polymer layers at the surface. However, the neutron reflectivity data show that even though the concentration profile changes over time, the amount of polymer adsorbed remains constant. These results suggest that the slow kinetics observed in surface tension measurements are due to structural rearrangements in the adsorbed layer.