The invention relates to aqueous dispersions of organosilicon compounds, preparation and application thereof, especially for the hydrophobing impregnation and mass hydrophobing of mineral and organic building materials, wherein the aqueous dispersions of organosilicon compounds contain: (A) as at least one organosilicon compound; (B) at least one nonionic emulsifier having an HLB value greater than or equal to 12, optionally as a mixture with nonionic emulsifiers having an HLB value of less than 12; (C) at least one cationic surfactant; (D) water, and optionally (E) other conventional components, wherin the (A) is selected from the following (A1) and (A2): (A1) silanes of the formula RaR<2>bSi(OR<1>)4-a-b (I) and/or the partial hydrolysis products thereof, (A2) siloxanes containing units R<3>c(R<4>O)dSiO(4-c-d)/2 (II), the C isselected from (C1) and (C2): (C1) R<9>cR<6>(4-e)N+X- (III), (C2) the compound of formula (IV), wherein the groups and indexes are defined as right claim 1. The compositions are especially useful for the hydrophobing impregnation and mass hydrophobing of mineral and organic building materials.