Hydrosilylation of aromatic aldehydes and acetophenone with H2SiPh2 was studied by using Pt complexes as the catalyst. Reaction of aromatic aldehydes, such as PhCHO, 4-FC6H4CHO, 4-MeC6H4CHO and 4-CF3C6H4CHO with H2SiPh2 in the presence of [Pt(PPh3)(3)] catalyst proceeds smoothly at room temperature with similar reaction rates. The hydrosilylation of PhCHO with H2Si(C6H4-4-Me)(2) proceeds faster than that with H2SiPh2. Comparison of the reactions of PhCHO with H2SiPh2 and with D2SiPh2 demonstrated a large kinetic isotope effect (3.1). The hydrosilylation of the aldehydes catalyzed by [Pt(PMe3)(mu-SiPh2)](3), reported in our previous paper, shows large dependence of the reaction rate on the aryl group of the substrate, in the order, 4-MeC6H4CHO >> PhCHO = 4-FC6H4CHO > 4-CF3C6H4CHO. Hydrosilylation of (3-vinyl) benzaldehyde and 10-undecenal in the presence of [Pt(PPh3)(3)] catalyst occurs at the carbonyl group selectively to form the corresponding alkoxysilanes. The hydrosilylation of acetophenone with H2SiPh2 catalyzed by [Pt(PPh3)(3)] forms 1-phenylethyl(diphenylsilyl) ether, while the reaction using the Pt-3 catalyst is accompanied by dehydrosilylation to yield a mixture of the saturated and unsaturated silyl ethers.