Cornelis Lehment studied at Hamburg University and for his PhD completed a thesis on the financial framework for public broadcasting. He qualified as a lawyer with a predicate exam in 1994 and started his professional career in the IP department of Boden Oppenhoff. After completing internal stages in Leipzig and Frankfurt, Dr Lehment moved to the Berlin office of Oppenhoff Rädler, where he practised intellectual property with a focus on unfair competition and media law. He left the firm in 2000 when it merged with Linklaters to establish a high-end IP boutique without the restraints and conflicts of a multinational firm. After a few years of working as a sole practitioner, Dr Lehment founded Lubberger Lehment with Dr Andreas Lubberger in 2004.

Dr Lehment specialises in trademark and unfair competition litigation, and cases of his before the Federal Court have influenced several aspects of the law concerning the press distribution and selective distribution systems. Within Lubberger Lehment, Dr Lehment has developed a specialisation in media and publishing law.

Dr Lehment regularly contributes to German IP law magazines and books. He is a board member of the Berlin section of the German Association for the Protection of Intellectual Property and advises the German Brand Association.