Hillenaar Outdoor Advertising develops outdoor media such as Billboards, several Street furniture formats, CityCells, Vensters®, Q-Park panels and Highway signs. Hillenaar is currently in the top three of outdoor advertising companies in the Netherlands and is also a major player in the indoor market. The company focuses its indoor media mainly on the younger target groups and provides poster panels in various formats to secondary schools, third level colleges, universities and grand cafés.

Hillenaar is a closed partnership set up on 1 November 1990. At present about sixty people work at the main office in Oegstgeest. In addition there are around thirty-five employees throughout the country who are responsible for changing the posters, placing and cleaning the advertising panels and various maintenance tasks.