Picture of Willem Hoorneman

Willem Hoorneman

Managing Partner

Atrium - Parnassusweg 737
1077 DG Amsterdam
PO Box 94700
1090 GS Amsterdam
Languages English, Dutch

Willem Hoorneman is a partner with CMS Netherlands and a member of the IP/TMC Practice Group. With more than 25 years of experience in IP and author of the patent chapters in the leading handbook on software protection in the Netherlands, Willem is considered a pre-eminent IP lawyer, and one of the very best in the field of patent law. 

Willem has earned an excellent reputation both as a litigator and a legal advisor on the marketing of inventions, whether those under patent or not, with extensive experience in the areas of contracting and licensing. As a specialist with a general civil law background, Willem is able to see the big picture and he focuses his efforts on coming up with creative, yet pragmatic solutions. 

Willem heads the IP team – as well as the Life Sciences Group – with the drive, energy and commitment which made clients recognise him in Chambers as “bringing to the table not only accurate and professional legal advice, but also a clear sense of strategy” (2010) and as being “responsive and plain-speaking” (2011).

IAM Patent 1000 2013: "Experienced life sciences expert Willem Hoorneman heads the IP team at CMS Derks Star Busmann, and is highly valued as a patent litigator and all-round counsellor. A broad civil law background gives him a fresh, commercial perspective on IP matters".  

Chambers 2014: Willem Hoorneman has wide-reaching IP expertise and wins praise from clients: “he is a very experienced lawyer with good business sense”.

Chambers Global 2015: “Department head Willem Hoorneman wins warm plaudits from sources for his patent work. Commentators agree he is ‘easy-going, highly knowledgeable and fast to act’.”

In addition to running his private practice, Willem is a domain name dispute resolution panellist with the World Intellectual Property Organization. For many years he has served as editor-in-chief of the BMM Bulletin (the Benelux Trademark and Design Journal).

more less

Practice head Willem Hoorneman of CMS is a ‘real expert’, praised for his ‘strategic’ work.

Legal 500, 2016

Clients describe him as "an excellent lawyer in this field, with good knowledge; an expert."

Chambers Global, 2016

Willem Hoorneman offers strong experience in patent law as well as handling many other general intellectual property issues.

Chambers Global, 2017


  • Dutch Law, University of Amsterdam

more less


  • Head of CMS Lifesciences Sector Group

  • Managing Partner

more less


Show only
Mov­ing times
Con­tinu­ity and sta­bil­ity are vi­tal when it comes to...
11 Dec 17
We­bin­ar: Lifes­ci­ences & Health­care - Up­date on the...
Ap­point­ments at CMS: COO and head HRM
30 Nov 17
We­bin­ar: Lifes­ci­ences & Health­care - The New EU Med­ic­al...
CMS Neth­er­lands elects a new board of dir­ect­ors and...
03 Nov 17
We­bin­ar: Lifes­ci­ences & Health­care - Up­date on SPCs
CMS rank­ings Cham­bers Glob­al 2016
CMS Glob­al Lifes­ci­ences For­um 2015
Shap­ing the fu­ture through in­nov­a­tion and col­lab­or­a­tion
CMS Glob­al Lifes­ci­ences For­um 2015 in Frank­furt
CJEU paves the way for longer SPC terms: the Seattle...
Dis­tri­bu­tion and mar­ket­ing of drugs in The Neth­er­lands
Em­ploy­ees' In­tel­lec­tu­al Prop­erty Rights: Part IIA:...
De lifes­ci­ences- en zorgsect­or: kwets­baar voor datalekken...
CMS lis­ted in the Cham­bers Europe 2015
Un­der the Mi­cro­scope
How 2014’s leg­al de­vel­op­ments could af­fect Lifes­ci­ence...
Kri­eno A. Fik­kert (67) Of Coun­sel for CMS
Tak­ing the Pulse of the Glob­al Life Sci­ences In­dustry
Nieuw: CMS Pat­ent Lit­ig­a­tion Guide / CMS web­site Pat­ents...