The migration of electronic excitation energy over the triplet levels of benzaldehyde in an ethanol solution in porous soda-borosilicate glass and matrix porous glass- polymethylmetacrylate is studied by capture in traps under steady-state excitation conditions. The probability of excitation capture by a trap as a function of donor concentration is obtained for different trap concentrations and temperatures. The change of the character of these dependencies without the change of the critical concentration value for benzaldehyde in matrix ethanol- porous glass is observed. The strong increase of the critical concentration of benzaldehyde in the matrix polymethylmetacrylate-porous glass takes place. The experimental result are analyzed in the framework of percolation theory.