More than half of large digital transformation projects in business practice fail to achieve their predefined goals. One major reason for failure is a lack of readiness. The problem lies in estimating the level of readiness. Existing approaches to evaluating companies' readiness for digital transformation are different and don't contain the justification of readiness criteria. The goal of this study is to determine the domains of a model for assessing companies' readiness for digital transformation by analyzing best practices. The article presents the results of analysis successful Russian companies implementing complex, large digital transformation projects. The study confirmed the hypothesis of the presence of typical areas of change for companies before implementing projects on digital transformation. To clarify the key areas of change and model's domain allocation, an analysis of modern management methodologies has been conducted. The distinguished domains are «Systematic management», «Business processes», «Human resource readiness», «Data management» and «Enterprise architecture».