This research is intended to carry out a comparative study between key successes factors of Six Sigma implementation in manufacturing and service companies in Uzbekistan and develop a capability model of Six Sigma implementation. In the intense competitive environment with customer demanding higher quality products and services, companies look for ways to improve their operational performance to respond to customer expectations. There has been a significant increase in the application of Six Sigma in industry over the past decade. Success stories of organisations that implemented Six Sigma and reaped huge benefits are generating a rising interest of many CEOs and organisations. Organisations need to have a Road Map (a capability model) for Six Sigma implementation before embarking on Six Sigma programmes. Data were collected from a sample of 107 companies in Uzbekistan selected at a random. The research findings showed that key success factors of Six Sigma implementation differ between manufacturing and service companies. Top management factor had been shown to have insignificant impact on success of Six Sigma implementation.