When does a very powerful company abuse its market power? What are the criteria that competition authorities use to distinguish between lawful and abusive practices by dominant firms, like digital giants? Renato Ferrandi, the co-ordinator of the OECD-GVH Regional Centre for Competition, answers these questions together with James Mancini, OECD competition experts, and Márk Pánczél, Head of the Antitrust Section of the Hungarian GVH.