Business model innovation (BMI) has become increasingly important, especially with fast changing business environment. While large enterprises approach these changes more or less systematically, small and medium sized enterprises (SMEs) are left to their own resourcefulness. For the purpose of developing dedicated methods and tools to support different SMEs in addressing these challenges, we have conducted a multiple case study to identify drivers behind BMI. We propose an analysis framework and present the results of four Slovene SME cases analyses. The results show that all four enterprises have made changes of the business model elements, some even new value proposition. The findings revealed differences between companies regarding the drivers behind BMI and changes of the different BMI elements. Two of four analysed companies see only opportunities while other two companies also struggles with internal or external threats. Overall, the results suggest all four SMEs, coming from different sectors, are facing BMI challenges without systematically addressing it and without using any dedicated BM ontologies or tools. The number of case studies included in the research is the major limitation of the study.