ZSM-22 zeolite catalysts modified with different contents of SiO_2 or La_2O_3 were prepared by impregnation method. Methylation of toluene with methanol to p-xylene was carried out over these catalysts by means of a fix-bed flow reactor. The results showed that selectivity to p-xylene was higher than m-and o-isomers over ZSM-22 catalysts. The modified catalysts exhibited higher selectivity to p-xylene but lower toluene conversion than ZSM-22. Toluene conversion declined while selectivity to p-xylene increased with SiO_2 or La_2O_3 content. ZSM-22 catalysts modified by La_2O_3 had the most remarkable increase in selectivity. Toluene conversion over ZSM-22 modified by La_2O_3 and SiO_2 combined was higher than over those modified solely by La_2O_3, while selectivity to p-xylene was comparable in both ease, with slight increase in selectivity to xylene.