Time-resolved photoluminescence study is carried out on ZnCdSe quantum dots (QDs) that are spontaneously formed on cleavage-induced fresh ZnSe (110) surface. Both rise and decay times show dependence on QD sizes. The size dependence of rise time is explained by the carrier capture from the ZnSe barrier into the QDs, which is determined by the overlap between the wave Functions of the QD state and the barrier state. On the other hand, the decay time is interpreted by taking into account the electron-hole separation and the overlap between the wave functions of the electrons and the holes.