Companies are facing increasing requirements for adaptivity and flexibility but also for efficiency and cost-effectiveness. Information technology has become more complex and often limits a company s ability to change. IT governance and enterprise architecture (EA) are approaches intended to assist companies in ensuring value from IT and managing change. Service-oriented architecture (SOA) is a new design paradigm and a technical architecture. The study researched the aggregated adoptions of these innovations in large Finnish companies. The study attempts to answer the following research questions: 1) How widely is SOA adopted by top 50 Finnish companies and what are the companies perceptions of SOA characteristics? 2) What is the level of the companies IT governance capabilities and IT governance performance? 3) How mature is enterprise architecture in large Finnish companies? 4) Does the study suggest a relationship between an organization s IT governance capabilities, EA maturity and SOA adoption? The theoretical background of this dissertation relies on existing knowledge of IT governance, EA and SOA, and maturity models. The research framework is based on traditional and IT diffusion research literature. The main data-gathering method was survey, conducted as conversational telephone interviews. Statistical methods were used to assist in the data analysis. Yet, the main purpose of the study was to understand, interpret and explain IT governance, EA and SOA in large Finnish companies. The study found that the diffusion of IT governance has saturated, while EA and SOA have reached the late majority adoption phase. The wide-scale adoption rate of SOA is increasing; financial and insurance, ICT, and transportation and storage industries are among the early adopters. The study describes the differences in IT governance capabilities, EA maturity characteristics and SOA perceptions between SOA adopters and non-SOA adopters. The study found indications of a relationship between IT governance and EA; high EA maturity was found positively related with high IT governance performance. In addition, high EA maturity had a positive effect on many IT governance capabilities. The results of the study suggest that IT governance and EA can be regarded as prerequisites for assimilation of SOA; two thirds of companies at assimilation stage of SOA had adopted EA while the adoption rate for non-SOA adopters was found to be significantly lower.