The aim of this paper is to investigate how EU how EU state aid policy addresses the problem the problem of the additionality of state aid for research, development and innovation. The methods used include a literature review of both theoretical and practical studies and document analysis. The formalistic approach taken in the majority of cases in the ex-ante state aid control requires further studies on the actual effects of implemented state aid measures. A variety of methods have been developed to identify the causal impact of aid and to address the problem of selection bias properly. Recent studies largely apply propensity score matching and strive to identify different types of additionality as well as the relationships between them, acknowledging that behavioural additionality plays a critical role in understanding the long-term impact of public interventions.