The kinetics of the free radical polymerization in supercritical carbon dioxide of third (G3) and fourth (G4) generation spacerless dendronized macromonomers, bearing a methacrylate group at the focal point, is experimentally investigated. Conversions up to 90% could be achieved in few hours for both monomers, with degrees of polymerization on the order of thousands of monomer units for G3 and 100-200 for G4. Experimental data are interpreted using a conventional free radical kinetic scheme. Within this frame, chain termination is dominated by chain transfer to monomer and the extremely high reactivity of the macromonomers when polymerized in supercritical carbon dioxide is reflecting reduced termination rate at increasing dendron generation.