When academic spin-offs are compared with other research- and knowledge-intensive start-ups, it is apparent that spin-offs are significantly more research- and knowledge-oriented than other start-ups. This fact is expressed for example in their higher research intensity, their higher inclination to patenting and their more intensive contacts to science. Spin-offs fill a particularly research-intensive segment within the research- and knowledge-intensive sectors and establish a connection between science and market. Nevertheless, econometric model calculations show that spin-offs are economically not more successful (as for turnover and employment growth) than other start-ups in the research- and knowledge-intensive sectors.