The present invention relates to substituted 5-phenyl pyrimidines I, which carry a radical X in the 4-position of the pyrimidine ring, a radical Y in the 6-position of the pyrimidine ring, the radical X denoting a group of the formula NR1R2, OR1a or SR1a, in which R1, R2, independently of each other, denote hydrogen, C1-C10-alkyl, C2-C6-alkenyl, C2-C6-alkynyl, C1-C10-haloalkyl, C3-C8-cycloalkyl, C3-C8-halocycloalkyl, phenyl, or 5- or 6-membered heteroaryl or 5- or 6-membered heterocyclyl, containing 1, 2, 3 or 4 nitrogen atoms or 1, 2 or 3 nitrogen atoms and one sulfur or oxygen atom as ring members, which radicals may be unsubstituted or may carry 1, 2, 3 or 4 radicals Ra1; or the radical NR1R2 may also form a 5- or 6-membered optionally substituted heterocyclic ring, containing 1, 2, 3 or 4 nitrogen atoms or 1, 2 or 3 nitrogen atoms and one sulfur or oxygen atom as ring members, which are non-adjacent to the nitrogen of NR1R2, in which two adjacent C atoms or one N atom and one adjacent C atom can be linked by a C1-C4-alkylene chain and wherein the heterocyclic ring may be unsubstituted or may carry 1, 2, 3 or 4 radicals Ra1 as defined in claim 1, R1a has one of the meanings given for R1 except for hydrogen; the radical Y being selected from the group consisting of halogen, cyano, C1-C4-alkyl, C2-C4-alkenyl, C2-C4-alkynyl, C3-C6-cycloalkyl, C1-C4-alkoxy, C3-C4-alkenyloxy, C3-C4-alkynyloxy, C1-C6-alkylthio, di-(C1-C6-alkyl)amino or C1-C6-alkylamino, where the alkyl, alkenyl and alkynyl radicals of Y may be substituted by halogen, cyano, nitro, C1-C2-alkoxy or C1-C4-alkoxycarbonyl; and wherein the pyrimidine radical may also carry a radical different from hydrogen in the 2-position and wherein the phenyl ring in the 5-position of the pyrimidine ring may be unsubstituted or carry 1, 2, 3, 4 or 5 radicals L which are different from hydrogen, and the pharmaceutically acceptable salts substituted 5-phenyl pyrimidines for use in therapy, in particular in therapy or treatment of cancerous diseases.