Half titanocenes (CpCH2CH2O)TiCl2 (1), (CpCH2CH2OCH3)TiCl3 (2), and CpTiCl3 (3), activated by methylaluminoxane (MAO) were able to give copolymerization of ethylene with internal olefins (i.e. cyclopentene, E and Z, –2-butene). 13C NMR analysis of obtained copolymers showed that the catalytic systems have low regiospecificity. In fact, in ethylene-–cyclopentene copolymers cyclic monomer insert with both 1,2 and 1,3-enchainment. In ethylene-2-butene copolymers 2-3, 1-3, and 1-2 insertion of 2-butene were detected. Differential scanning calorimetry and X-ray powder diffraction analysis proved that the copolymers are crystalline.