Abstract. This paper examines the use of surveys in measuring privacy concerns in ubiquitous computing environments. Two evaluation techniques are used to study the privacy concerns of sharing context information: a paper based survey and in-situ questionnaires. Results from the two techniques differ significantly, suggesting that surveys are not reliable in predicting privacy concerns regarding context-aware services. Further, the surveys are not consistently biased; for some information, people shared more in-situ than they predicted they would share in the survey, while for other types, they shared less.