A local bond-polarization model based on the displacement-displacement Green's function and the Born potential are applied to study the confined optical phonons and Raman scattering of diamond nanowires (DNWs). Also, the electronic band structure of DNWs are investigated by means of a semi-empirical tight-binding approach and compared with density functional theory within local density approximation. The supercell technique is applied to model DNWs along [001] direction preserving the crystalline diamond atomic structure. The results of both phonons and electrons show a clear quantum confinement signature. Moreover, the highest energy Raman peak shows a shift towards low frequencies respect to the bulk crystalline diamond, in agreement with experimental data.