Abstract: A method of treating ADHD comprising administering a 5-HT6 receptor antagonist according to formula (A) hereinbelow: wherein: P is phenyl, naphthyl, a bicyclic heterocyclic ring or is a 5 to 7-membered heterocyclic ring each containing 1 to 4 heteroatoms selected from oxygen, nitrogen or sulphur; A is a single bond, a C1-6alkylene or a C1-6alkenylene group; R1 is halogen, C1-6alkyl optionally substituted by one or more halogen atoms, C3-6cycloalkyl, C1-6alkoxy, OCF3, hydroxy, hydroxyC1-6alkyl, hydroxyC1-6alkoxy, C1-6alkoxyC1-6alkoxy, C1-6alkanoyl, nitro, amino, C1-6alkylamino or diC1-6alkylamino, cyano or R1 is phenyl, naphthyl, a bicyclic heterocyclic ring or is a 5 to 7-membered heterocyclic ring each containing 1 to 4 heteroatoms selected from oxygen, nitrogen or sulphur; n is 0, 1, 2, 3, 4, 5 or 6, R2 is hydrogen, C1-6 alkyl or aryl C1-6 alkyl; R3 is a group R5 or together with R5 forms a group (CH2)2O or (CH2)3O or R3 is linked to R2 to form a group (CH2)2 or (CH2)3; R4 is &mdash