The present invention relates to novel quinoline compounds. The compounds possess valuable therapeutic properties and are particularly suitable, for treating diseases that respond to modulation of the serotonin 5-HT6 receptor. wherein R is a moiety of the formula wherein A, R1 to R4 are as defined in the claims and the specification, n is 0, 1 or 2; m is 0, 1, 2 or 3; Ra, Rb are independently selected from the group consisting of halogen, CN, C1-C4-alkyl, C1-C4-haloalkyl, C1-C4-alkoxy, C1-C4-haloalkoxy, C(O)Raa, C(O)NRccRbb and NRccRbb; X is CH2, C(O), S, S(O) or S(O)2; which is located in the 3- or 4-position of the quinoline ring; Ar is a radical Ar1, Ar2—Ar3 or Ar2—O—Ar3, wherein Ar1, Ar2 and Ar3 are each independently selected from the group consisting of aryl or hetaryl wherein aryl or hetaryl moieties may be unsubstituted or may carry 1, 2, 3 substituents Rx, wherein and physiologically tolerated acid addition salts and the N-oxides thereof.