Most porous Si materials studied have been oxidized in various degrees. The oxidized porous Si comprises of a great quantity of nanoscale Si particles (NSPs) and each of them is covered by a Si oxide layer. The structure and luminescence properties of the NSPs embedded Si oxide and the nanoscale Si/nanoscale SiO2 multilayers are similar to those of the oxidized porous Si. All the three kinds of materials mentioned are called nanoscale Si/Si oxide materials and their photoluminescence and electroluminescence properties especially light emission mechanisms are reviewed in this article. Nanoscale Si/Si oxide materials have been well studied and are believed to be very promising Si based light emitting materials. The very distinct roles of the NSPs and the luminescence centers in Si oxide in the photoluminescence and electroluminescence from the nanoscale Si/Si oxide materials are highlighted.