The knowledge of opinion leaders (in their area of interest) to a certain extent has always been taken for granted by communication scholars. This article investigates what opinion leaders really know. Two studies will be presented to answer the above question. Participants (N = 119) of the first study were assessed according to ratings on three scales of opinion leadership (Katz and Lazarsfeld, Personal influence. The part played by people in the flow of mass communication, Free Press, 1955; Troldahl and van Dam, Journalism Quarterly 42: 655–657, 1965; Childers, Journal of Marketing Research: 184–188, 1986), personality strength (Noelle-Neumann, Persönlichkeitsstärke, Der Spiegel, 1983) and political knowledge. In the second study, respondents (N = 727) were assessed according to ratings of opinion leadership (Childers, Journal of Marketing Research: 184–188, 1986) and political knowledge. In both studies, it was found that opinion leaders can be divided into ‘informed opinion leaders’, who know a lot in their area of interest, and ‘uninformed opinion leaders’, who are ill-informed about the field they claim as theirs. In both studies ‘informed opinion leaders’ read newspapers approximately one hour longer per week than ‘uninformed opinion leaders’.