The energy transition process has a significant impact on the energy distribution grid through an increasing decentralisation and electrification of energy resources. Digitalisation offers opportunities to support security and quality of supply in the transition process. Distribution System Operators (DSOs) need to embrace the opportunities and change their operating paradigm by leveraging on the digital solutions. This study aims to shed light on the barriers for the DSOs digitalisation process. We develop a conceptual framework that systematically links perceived or observed barriers to digital technologies and DSOs core functionalities. We identify six DSOs core functionalities that need to be improved by means of digital investments and map key implementation barriers building on a comprehensive and multi-disciplinary literature review. This cross-featuring sheds new light on the nature of best practices that can alleviate digitalisation barriers associated with various DSOs functionalities.