Purpose: This paper aims to review 68 archival studies on the impact of audit committees (ACs) on firms’ consequences [(non)financial reporting, performance and audit quality] in European firms. Design/methodology/approach: Applying a stakeholder agency-theoretical framework, the author differentiates between three categories of AC variables: presence; composition; and resources, incentives and diligence. Findings: The author finds that AC composition, (non)financial reporting and audit quality are dominant in the literature review. Other inputs or outputs are either too low in amount or yielded heterogeneous results, hindering clear tendencies. However, there are indications that financial expertise is positively related to financial reporting and audit quality, in line with agency theory and European regulatory assumptions. Research limitations/implications: In the discussion of potential future research, the author emphasizes, among others, the need for the recognition of innovative and sustainable AC variables, inclusion of moderator and especially mediator variables and reaction to endogeneity concerns by advanced regression models. Practical implications: As the European Commission currently discusses extended regulations on AC duties and composition, this literature review highlights the huge impact of financial expertise on financial reporting and audit quality. In view of the increased monitoring duties of sustainability reporting, both business practices and regulatory bodies should increase the sustainability expertise of ACs. Originality/value: This analysis makes useful contributions to prior research by focusing on attributes of AC and their impact on firms’ outputs in the European capital market, based on a differentiation between mandatory one-tier/two-tier systems and the choice model. The findings support the promotion of European evidence-based regulations, such as the Corporate Sustainability Reporting Directive and the Corporate Sustainability Due Diligence Directive.