We present depth-resolved positron 2D angular correlation of annihilation radiation (2DACAR) experiments on CdSe quantum dots in the diameter range from 2.5 to 6 run, deposited as micrometer thin layers. The average radial distribution of the valence electron momentum density (EMD) of CdSe quantum dots so extracted reveals a systematic dependence upon particle size. The observed quantum confinement related changes near the Jones zone momentum of similar to0.8 a.u. agree with our earlier coincidence Doppler study addressing this point. We focus here on the behavior of the average radial EMD, which is found to show an increase in the low-momentum range (<0.6 a.u.) and a reduction in the high-momentum range (>1.6 a.u.) with respect to that measured on a bulk CdSe single crystal. First-principles calculations based on the Koninga-Kohn-Rostoker (KKR) method were performed to gain insight into this effect.