The selection process is a crucial activity of the development of COTS-based systems. A key step of the evaluation of COTS components carried out during selection is the matching between user requirements and COTS features. We propose a goal-based approach to guide the matching process, using quality models for leveraging goals and COTS features. The different mismatch situations that may arise are reasoned by means of exploratory scenarios. We demonstrate the approach with the mail server case study.