PtI2(PPh3)(2) catalyzes hydrosilylation of 2,2-diphenyl-1-methylenecyclopropane with HSiEt3, HSiPh3, HSiEt2Ph, HSiPhCl2, and HSiCl3 under solvent-free conditions at 140 degreesC to produce the silyl compounds with a (2,2-diphenyleyclopropyl)methyl substituent in moderate to high yields without ring-opening of the substrate. PtI2(PPh3)(2) is converted by the reaction into PtH(I)(PPh3)(2), which also catalyzes the hydrosilylation of the methylenecyclopropanes. The reaction of 2-phenyl-1-methylenecyclopropane, 2-methyl-2-phenyl-1-methylenecyclopropane, 2,2-diphenethyl-1-methyl-enecyclopropane, and alkylidenecyclopropanes with HSiEt3 catalyzed by PtI2(PPh3)(2) causes addition of hydrosilane to the substrate accompanied by ring-opening. 2,2-Diphenyl-1-methylenecyclopropane undergoes ring-opening isomerization in the presence of HSi(OEt)Me-2 and Pt(PEt3)(3) catalyst to give 1,1-diphenyl-1,3-butadiene. The pathways for the hydrosilylation and the isomerization are discussed.