The paper highlights the role of non functional information (about efficiency, reliability and other software attributes) of software components in software maintenance, focusing in the component programming framework. Non functional information is encapsulated in modules bound to both definitions and implementations of software components and it is written as expressions in a classical programming language. It is shown with an example how this notation supports software maintenance, with the help of an algorithm which is able to select the best implementation of a software component in its context of use, meaning by "best" the one that better fits to its non functional requirements. As a conclusion, we may say that our proposal will probably reduce maintenance costs in case of software modifications due to changes in the non functional environment of the system and also to changes in the NF behaviour of software components, including migration to other platforms.