Difluorocarbene, CF 2, generated by thermal decomposition of Cf 3SiF 3 at 100°C, has been found to insert into the SiH bonds of halosilanes SiH 3X (X = F, Cl, Br, I), methylhalosilanes CH 3SiH 2X (X = Br, Cl) and (CH 3) 2SiHCl, and disiloxane (SiH 3) 2O. Use of excess of the CF 2-source CF 3SiF 3 and of pressure favour the formation of the di-insertion products (CHF 2) 2SiHX and (CHF 2) 2(CH 3)SiX. (CHF 2) 3SiCl was identified among the products formed in the co-thermolysis of CF 3SiF 3 and (CHF 2)SiH 2Cl. In contrast, organosilanes R n SiH 4− n (R = Me, Ph; n = 0–4), dihalosilanes SiH 2X 2 and RSiHX 2, trihalosilanes HSiX 3 and tetrahalosilanes SiX 4 do not react with CF 2 under theseconditions. The reactivity and selectivity of difluorocarbene is discussed in terms of steric and electronic parameters. A kinetic deuterium effect, k(SiH)/ k(SiD) 1.14 has been observed for the insertion into MeSiH 2Cl. The mostly novel products were characterized by vibrational and multinuclear NMR spectroscopy. Difluoromethylsilane, (CHF 2)siH 3, has been obtained from (CHF 2)SiH 2Cl and LiAlH 4 in almost quantitative yield, and its vibrational spectrum has been recorded and interpreted with the assistance of a normal coordinate analysis.