An investigation of Raman scattering in CdSe nanocrystals embedded in oxide glass matrix under resonant excitation has been accomplished. First we observe the dependence of both the longitudinal optical phonon and the low frequency scattering energies with the excitation wavelength which is explained in terms of size selective excitation. A peculiar attention is given to the behaviour of low-frequency spectra and selection rules due to resonance effects are reported. Most of the first harmonics of the different predicted vibration modes have been observed and a qualitative attempt has been made to link the observed modes with the excited electronic levels.