The invention relates to novel 7,8,9,10-tetrahydro-6H-azepino, 6,7,8,9-tetrahydro-pyrido and 2,3-dihydro-2H-pyrrolo[2,1-b]-quinazolinone derivatives and their use as active ingredients in the preparation of pharmaceutical compositions. The invention also concerns related aspects including processes for the preparation of the compounds, pharmaceutical compositions containing one or more of those compounds and especially their use as orexin receptor antagonists.