Quinolin-2-ones bearing a heteroaryl-piperazine linked by a two carbon chain at the 3-or 4- position were synthesised and evaluated as mixed 5-HT1B/5-HT2A receptor antagonists. Potent mixed antagonists were obtained with thieno [3, 2-c] pyridine derivatives. In this series, compound 2.1 (SL 65.0472) proved to be functional antagonist at both the 5-HT2A receptor (rat in vivo 5-HT-induced hypertension model) and the 5-HT1B receptor (dog in ...