Enterprise systems should be assembled out of components and services according to an orchestration schema and taking into account not only functional requirements but also the resulting Quality of Service (QoS). In other words, QoS-aware composition of services and components must be performed. The problem is to find which components or services have to be employed that the resulting system would optimize some QoS attributes while satisfying some other QoS constraints. The paper proposes to use the Constraint Logic Programming approach to solve this problem, that is, we see this problem as a discrete optimization and satisfaction problem.