Purpose – The activity-based office concept of the modern office 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 added value, there is still a need for sound data on the relationship between office design, its intentions and the actual use after implementation. The purpose of this paper is to address this issue. Design/methodology/approach – An evaluative study on the effectiveness of activity-based office concepts was carried out to gain more insight in their use. The study included relevant literature on workplace design, combined with an observation and a survey of 182 end-users from four different service organizations in The Netherlands. Findings – The findings from these case studies underline some known benefits and disadvantages of activity-based office concepts, and provide insight in the importance of several physical, social and mental aspects of the office environment in employee choice behavior. This study shows that the office concept is not always used as intended what could result in a loss in productivity, illness and dissatisfaction. People's personal preferences seem to have a bigger effect on the use of certain types of workplaces than some workstation facilities, although ergonomics and IT equipment and systems are expected to be satisfactory everywhere. Misusage of the concept is often the consequence of critical design (process) failures. Originality/value – The originality of this research lies in the combination of studying the program of requirements, a questionnaire and most of all the observation in a quiet period, providing new information on choice behavior.