Content-based Image Retrieval systems (CBIRS) start flourishing on the Web. Their performances are continuously improving and their base principles span a wide range of diversity. Content-based Video Retrieval systems (CBVRS) are less common and seem at a first glance to be a natural extension of CBIRS. In this document, we summarise advances made in the development of CBVRS and analyse their relationship to CBIRS. While doing so, we show that CBVRS are actually not so obvious extensions of CBIRS. (40 References)