This expanding use of AI systems raises discussions about their risks, such as non-transparent decision-making processes, discrimination, increasing energy consumption and greenhouse gas emissions or increasing consumption, e.g., through personalised advertising. This talk presents preliminary insights from the project “SustAIn – Sustainability Index for Artificial Intelligence”, which aims at developing a comprehensive framework for assessing AI systems from a sustainability perspective. We outline conceptual considerations for establishing a comprehensive set of criteria that can be deployed in order to minimise negative social, ecological and economic impacts of AI-Systems and their applications. To develop a comprehensive assessment framework, we distinguish between the different scopes of impacts related to AI and we define sustainable AI maturity levels. We outline how we can define measures for each of the above criteria that need to be implemented to enhance the sustainability of AI systems.