This thesis empirically assesses the economic relevance of investor relations (IR) quality in listed companies that are subject to different legal and financial systems. The empirical study relies on a proprietary panel data for German and UK firms for the time period from 2006 to 2014. An analysis is first conducted with regard to firm performance, stock liquidity, stock volatility, capital costs, and analysts’ forecast characteristics. The impact of IR quality on M&A and SEO performance in both countries is also analyzed. In summary, this thesis identifies significant differences with respect to the relevance of IR in the two markets investigated and it offers new and fundamental insights into the value of corporate communication with financial markets.