Addition of polymer to colloidal suspensions induces an attractive part to the colloid pair potential, which is of purely entropic origin ("depletion interaction"). We investigated the influence of polymer branching on depletion forces by studying mixtures of hard sphere colloids and star polymers with increasing arm number f=2-32, but constant Rg귔 . We found a pronounced effect of branching on the position of the gas/liquid demixing transition. Using small angle neutron scattering (SANS) we were able to measure partial structure factors in star polymer/colloid mixtures. The relative distance to the demixing transition is reflected in our scattering data.