During the COVID-19 pandemic, perception surveys suggest that the public gained trust in scientists and their jobs, but not without some initial doubts. The uncertainties of science can be hard to communicate and, especially in connection with health, scientists must consider what makes the public trust them. To understand in whom the public trust as sources of scientific information, a survey was conducted among engineering and science students and teachers in Portugal. Although the results are not representative of society, but only a qualified segment, some patterns can be inferred that are not so different from the results that Portuguese society as such showed in the last Eurobarometer, which will constitute comparative material in this chapter. The results of this study show that students and teachers give similar answers, despite age and career differences, and that they largely trust scientists from universities, public research institutes and private companies. It is also clear that they do not trust politicians or the military as the rest of Portuguese society on science and technology does. In the present chapter, it is argued that science communication can play an important role in building relationships of trust between experts and audiences.