A liquid crystal medium with positive dielectric anisotropy comprising one or more compounds selected from formulae Y, CY, PY and LY, and one or more compounds of formula S1 and one or more compounds of formula S2 wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings: with at least one ring F being cyclohexenylene, R 1, R 2 alkyl having 1 to 12 C atoms, where, in addition, one or two non-adjacent CH 2 groups may be replaced by -O-,-CH=CH-, -CO-, -OCO- or -COO- in such a way that O atoms are not linked directly to one another, Z x, Z y -CH 2 CH 2 -, -CH=CH-, -CF 2 O-, -OCF 2 -, -CH 2 O-, -OCH 2 -,-CO-O-, -O-CO-, -C 2 F 4 -, -CF=CF-, -CH=CH-CH 2 O- or a single bond, L 1-4 F, Cl, OCF 3, CF 3, CH 3, CH 2 F, CHF 2, R a-d straight chain or branched alkyl with 1 to 10 C atoms, X H, CH 3, OH or O•, A straight-chain, branched or cyclic alkylene with 1 to 20 C-atoms which is optionally substituted, a 1 or 2, b 0 or1, f 1 or 2, n an integer from 1 to 6, with the proviso that the media having the following compositions are excluded: 1) a medium having the following composition: APUQU-2-F 2.50 % CC-3-2V1 5.00 % CC-3-V 24.50 % CC-3-V1 5.00 % CCP-3OCF 3 3.00 % CCP-V-1 9.00 % CCP-V2-1 8.00 % CLP-3-T 7.00 % CPGP-4-3 2.00 % DGUQU-4-F 5.00 % DPGU-4-F 5.50 % PGP-2-2V 2.00 % PGUQU-3-F 6.00 % PGUQU-4-F 6.00 % PPGU-3-F 0.50 % Y-4O-O4 9.00 % which is additionally stabilised with 0.04% of the compound of the formula S2-1a and with 0.02% of the compound of the formula S1-2a 2) a medium having the following composition: CC-3-V 49.00 % CC-3-V1 12.00 % CCP-V-1 10.00 % CLP-V-1 7.00 % PGP-2-2V 5.50 % CLP-3-T 4.00 % PGUQU-3-F 3.00 % APUQU-2-F 6.00 % PP-1-2V1 3.00 % PPGU-3-F 0.50 % which is additionally stabilised with the compound of formula S2-1a and, in addition, with the compound S1-1a or with the compound S1-2a shown above in the amounts given in the following table: S2-1a S1-1a S1-2a 400 ppm 100 ppm - 400 ppm 500 ppm - 400 ppm 1000 ppm - 400 ppm - 100 ppm 400 ppm - 500 ppm 400 ppm - 1000 ppm R 1, R 2 alkyl having 1 to 12 C atoms, where, in addition, one or two non-adjacent CH 2 groups may be replaced by -O-,-CH=CH-, -CO-, -OCO- or -COO- in such a way that O atoms are not linked directly to one another, Z x, Z y -CH 2 CH 2 -, -CH=CH-, -CF 2 O-, -OCF 2 -, -CH 2 O-, -OCH 2 -,-CO-O-, -O-CO-, -C 2 F 4 -, -CF=CF-, -CH=CH-CH 2 O- or a single bond, L 1-4 F, Cl, OCF 3, CF 3, CH 3, CH 2 F, CHF 2, R a-d straight chain or branched alkyl with 1 to 10 C atoms, X H, CH 3, OH or O•, A straight-chain, branched or cyclic alkylene with 1 to 20 C-atoms which is optionally substituted, a 1 or 2, b 0 or1, f 1 or 2, n an integer from 1 to 6, 1) a medium having the following composition: APUQU-2-F 2.50 % CC-3-2V1 5.00 % CC-3-V 24.50 % CC-3-V1 5.00 % CCP-3OCF 3 3.00 % CCP-V-1 9.00 % CCP-V2-1 8.00 % CLP-3-T 7.00 % CPGP-4-3 2.00 % DGUQU-4-F 5.00 % DPGU-4-F 5.50 % PGP-2-2V 2.00 % PGUQU-3-F 6.00 % PGUQU-4-F 6.00 % PPGU-3-F 0.50 % Y-4O-O4 9.00 % which is additionally stabilised with 0.04% of the compound of the formula S2-1a and with 0.02% of the compound of the formula S1-2a 2) a medium having the following composition: CC-3-V 49.00 % CC-3-V1 12.00 % CCP-V-1 10.00 % CLP-V-1 7.00 % PGP-2-2V 5.50 % CLP-3-T 4.00 % PGUQU-3-F 3.00 % APUQU-2-F 6.00 % PP-1-2V1 3.00 % PPGU-3-F 0.50 % which is additionally stabilised with the compound of formula S2-1a and, in addition, with the compound S1-1a or with the compound S1-2a shown above in the amounts given in the following table: S2-1a S1-1a S1-2a 400 ppm 100 ppm - 400 ppm 500 ppm - 400 ppm 1000 ppm - 400 ppm - 100 ppm 400 ppm - 500 ppm 400 ppm - 1000 ppm