Nanosheets, narrobelts, and ultralong nanobelt arrays with honeycomb-like micropatterns of ZnSe were synthesized via a solvothermal reaction of Zn with Se and KBH4 in ethylenediamine at 200 degrees C for 24 h and subsequent annealing. The control over these nanostructures with different morphologies was achieved by adjusting the KBH4/Se molar ratio. The role of KBH4 in the formation of ZnSe(en)(0.5) nanobelts with different length-to-width ratios was investigated, and a possible mechanism was also proposed to account for the growth and conversion of these precursor nanostructures into ZnSe nanostructures. Current-voltage behaviors of the ultralong nanobelt arrays with honeycomb-like micropatterns were investigated. In addition, variable-aspect ratio ZnS nanosheets and nanowires were also synthesized by adjusting the KBH4/thiourea molar ratio in the Zn-thiourea-KBH4-ethylenediamine solvothermal system. The results suggest that this method may be employed for the controllable synthesis of other II-VI semiconductor nanostructures such as ZnTe, NiS, MnS, and so forth and provides opportunities for both fundamental research and technological applications.