Attorney at law, Partner

Dennis Zieren


Dennis has a large knowledge and experience in drafting, reviewing  and negotiating all kind of IT contracts on behalf of serviceproviders as well as on behalf of customers. Dennis also often litigates in IT-disputes  in the Dutch courts and (IT) arbitration tribunals. Dennis is amongst others an active member of the Platform Outsourcing Netherlands (PON).

Public and Utilities Procurement Law, besides IT & Privacy Law, has become an important part of his law practice. The knowledge and experience of Dennis in this expertise is not limited to the IT-sector, but also includes other sectors as Construction, Energy, Education, Insurance and Healthcare. Furthermore, Dennis’s experience in Public and Utilities Procurement law is not limited to advising and litigating on regular public and utilities contracts, but also includes advising and litigating on Public and Utilities Procurement Law issues as concessions, In-house provision, Best Value Procurement, etc.

Dennis has completed two post graduate Grotius specialization programmes: Information Technology Law in 2002 and European and Dutch Procurement Law in 2009.

Dennis services a rather large amount of clients in the health sector and is therefore, beside his membership of the TM&T team, also  an active member of the Care Team of Ploum. In 2014 Dennis has become member of the Management board of Ploum.

Furthermore, Dennis has several additional functions; e.g. Dennis is member of the board of Children Rehabilitation Fund Adriaanstichting.

What clients say about me

‘The client service is always excellent, as is the quality of the advice. Dennis Zieren stands out. There is deep data privacy and data protection knowledge across the team. Client driven, focused and always there when you need them.’ - Legal 500 EMEA 2021

‘Dennis Zieren provides personal and to-the-point advice that is of great added value to the client. Go-to person for all our ICT law, privacy and data protection law matters. Easy to work with and very responsive.’ - Legal 500 EMEA 2021


Dennis (1970) graduated from Leiden University and has joined Ploum in 1999. Dennis has become a partner of Ploum in 2006. Before joining Ploum Dennis has worked as an in-house lawyer for the Royal Dutch Air Force and a major Dutch insurance company.

Starting from a broad commercial contracts and commercial litigation practice, Dennis has developed since 2000 an expertise in first IT & Privacy Law and later on Public and Utilities Procurement Law.


  • ‘Innovation in IT Outsourcing relations’, co-author (in Dutch), Platform Outsourcing Netherlands, 2014


  • ITechlaw
  • Nederlandse Vereniging voor Aanbestedingsrecht (NVvA), the Dutch Association for Procurement Law
  • Nederlandse Vereniging voor Informaticatechnologie en Recht (NVvIR), the Dutch Association for Information Technology and Law
  • Vereniging Privacy Recht (VPR), the Dutch Association for Privacy Law
  • Vereniging Informaticarecht Advocaten (VIRA), the Dutch Association for Information Technology Law

The Netherlands Bar’s register of legal practice areas (rechtsgebiedenregister)

Dennis Zieren has registered the following principal (and secondary) legal practice areas in the Netherlands Bar’s register of legal practice areas (rechtsgebiedenregister):

  • Procurement law (aanbestedingsrecht);
  • ICT law, sub legal practice area privacy law.

Based on this registration, Dennis Zieren is required to obtain ten training credits per calendar year in each registered principal legal practice area in accordance with the standards set by the Netherlands Bar.

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