European Union (EU) environmental policy can only work in practice when it is implemented by and within the member states. Yet, despite its importance, we still lack a solid and cumulative understanding of the practical implementation of EU environmental policies, mainly because of the dominance of case‐specific empirical insights and the dichotomous conceptualization of compliant implementation. This paper proposes a conceptual framework for analysing implementation performance, which is built around three dimensions: substance, scope and effort. The framework's relevance and analytical quality are substantiated by a systematic review of empirical studies on practical implementation of 18 EU environmental directives. We find evidence of three types of knowledge deficits: there is neglect of the ‘scope’ and ‘effort’ dimensions of implementation; disproportionate attention to the Water Framework Directive, and the Northern and Western European member states. The proposed conceptual framework aims to inform future research on EU environmental implementation. © 2017 The Authors. Environmental Policy and Governance published by ERP Environment and John Wiley & Sons Ltd