Privacy might be the greatest barrier to the longterm success of pervasive or ubiquitous computing (ubicomp). The invisibility of embedded computing devices has made it easier to collect and use information about individuals without their knowledge. Sensitive and private information might be stored for long periods of time and appear anywhere at anytime. Thus, a cost, in the form of privacy, might need to be paid to benefit from ubicomp. In this paper, we introduce the concept of Quality of Privacy (QoP) which allows balancing the trade-off between the amount of privacy a user is willing to concede and the value of the services that can be provided by a ubicomp application, in a similar way as that of Quality of Service (QoS). We propose an agent-based architecture that adapts the behavior of the ubicomp application to the users? context, in order to satisfy the level of QoP, that both, the application and the user have agreed upon. To illustrate this architecture, we extend a handheld-based mobile Hospital Information System in order to preserve privacy in a ubicomp hospitals environment.