Time-resolved investigation of deuterium-substituted silylene (SiD2) generated by laser flash photolysis of deuterium-substituted phenylsilane (PhSiD3) was carried out to obtain rate constants for its bimolecular reaction with ethylene (C2H4). The reaction was studied in the gas phase over the pressure range of 1-100 Torr (in SF6 bath gas) at 295 K The rate constants for SiD2 + C2H4 were found to be independent of pressure and close in magnitude to the rate constants for the reaction of SiH2 + C2H4 at the high-pressure limit. They are consistent with a rapid isotopic scrambling mechanism similar to that of SiH2 + C2D4. While silirane, the main product produced from this reaction, was too labile to be detected, vinylsilane, another possible product, was ruled out by gas chromatography analysis. This reaction shows similarities to those of SiH2 + H-2 and its isotopic counterparts.