Following to the increased size and complexity of software products, a single application is commonly made up of components produced by different developers using different practices. Components can be of different kinds: COTS (Commercial Off-the-Shelf), Open Source (OS), developed in-home, etc. Use of components places new questions and this paper determines a component?s maintainability through a framework for software components characterization. It supports a software engineer in selecting components to integrate in a software system. The framework includes three sets of characterization parameters: the first for all types of components; the second and third set for white box and OS components. The framework has been evaluated through an empirical study on two industrial projects. Results are interesting: several of the characteristics included in the framework are correlated and are unable to characterize the system maintainability. These findings seem disappointing although interesting and stimulate further research within component based development.