During our systematic studies on the arginine vasopressin receptor V1a-antagonistic activity of 1-(1-benzoyl substituted 4-piperidyl)-3, 4-dihydro-2(1H)-quinolinones, we found a general substituent effect on the benzene ring. Hydrogen-bonding ability at the ortho position was especially important for enhancement of the affinity of multi-substituted analogs. Details of the syntheses and structuer-activity relationships for this series are presented.