The modern office (design) serves a different function as twenty years ago. Not only does it reflect current social values but it also has evolved to accompany organizational changes and support New Ways of Working. This so-called activity-based office concept is set to increase productivity through the stimulation of interaction and communication while retaining employee satisfaction and reducing the accommodation costs. Although some research has gone into understanding the former, there is still a need for sound data on the relationship between office design and productivity. For this reason, an evaluative study on the effectiveness of activity-based office concepts was carried out to gain more insight in their use. The research methods consisted of a wide research of relevant literature on workplace design, both from environmental psychological and economical perspective, coupled with the collection and analysis of empirical data. The latter is based on both an observation and a survey of 182 end users from four different service organizations in the Netherlands, using questionnaires. The findings from these case studies underline some known benefits and disadvantages of activity-based office concepts. They provide insight in the importance of several physical, social and mental aspects of the office environment in employee choice behavior. The data from this research may be used by Corporate Real Estate Management (CREM) to support future decision making on accommodation policy.