The polymerization of 2-methylpropene in methylene dichloride can be initiated by 2-azido-2-phenylpropane (APP) in the presence of some Lewis acids. The system APP-boron trichloride gave only the usual polymer functionalization by a tertiary chloride at one chain end and the cumyl moiety at the other end. The system APP-antimony pentafluoride gave no significant functionalization. The system APP-titanium tetrachloride gave a polymer which was partly functionalized by an azide group. The system APP-boron trifluoride gave complete functionalization within experimental accuracy. These experiments show that, by cationic polymerization of 2-methylpropene and using the suitable initiator-Lewis acid combination, it is possible to obtain by direct synthesis from the monomer a polymer specificially functionalized by a carbon-to-nitrogen bond. Less specific functionalization is also possible in a nonpolar medium.