A variety of reference models such as CMMI, COBIT or ITIL supports IT organizations to improve their processes. Although these process improvement reference models (IRMs) cover different domains, they also share some similarities. There are organizations that address multiple domains under the guidance of different IRMs. As IRMs overlap in some processes and have inter-dependencies, we developed an approach to integrate multiple IRMs. This enables organizations to efficiently adopt and assess multiple IRMs by automatically identifying IRM similarities and their dependencies. In this paper, we give an overview of this approach and particularly focus on its evaluation.