In this study we investigate the deployment of a model for IT governance named pm in a large healthcare organisation. We are especially interested in if and how the basic goals, the inherent rationality, of the pm model-in-concept change in translation during the model deployment process. The concept of model rationality is suggested as a beneficial approach for analysing differences between pm3-in-concept and pm-in-use. We have identified three main contributions with the suggested approach that are of benefit for both research and practice: 1) We can define and express the rationality in the pm3 model for IT and governance in a clear manner, 2) we have used the pm3 rationality as an evaluation tool that has proven to be useful in practice, and 3) we have also identified the main problems in deploying pm in the investigated healthcare organisation.