One of the great challenges in the distributed enterprise computing is providing software systems with expected Quality-of-Service (QoS). For this purpose, it is very important to include QoS aspects in all the phases of the system development life cycle (analysis, design, deployment, etc.). This is enforced by the new approaches to system design, such as the model-driven approach called MDA (Model Driven Architecture). MDA is a modeling framework that improves the efficiency and decreases the complexity of the development of software system by allowing to model functional aspects independently of the underlying platform and the generation of its models in a target platform. In this context, this paper studies the model-driven development of distributed component-based software applications with QoS support, which includes QoS specification and QoS monitoring. The proposal consists of applying the MDA principles to specify QoS aspects of component-based applications in parallel to the traditional design of the functional aspects. For this purpose, we define the following elements: a) a QoS catalogue to characterize a software component from the QoS point of view; b) a UML profile for modeling QoS contracts of component-based applications, and c) a UML profile for modeling the monitoring mechanisms employed to monitor that QoS. In addition to the description of all these elements, the paper will introduce a real scenario in which the proposed ideas have been tested and partially validated.