Purpose– In most European code-law oriented Latin countries, the publication of a CEO's letter to shareholders in a company's annual report is a fairly recent phenomenon. In this paper, the authors seek to determine the characteristics that explain why companies in one such country, i.e. Portugal, published a CEO letter.Design/methodology/approach– The paper's holistic theoretical framework draws on elements of agency theory, institutional theory and signalling theory. To understand the characteristics of Portuguese holding companies that published CEO letters, the authors used a logistic regression model to explore 266 observations over the years 2006-2011.Findings– The publication of a CEO letter becomes more likely if a firm is audited by a Big 4 accounting firm; has a higher level of profitability; and has a high number of foreign subsidiaries. Other findings are that finance companies are slightly more likely to publish a CEO letter than non-finance companies. The number of CEO letters increased to a peak in 2008, and then declined.Practical implications– The increasing number of companies now publishing a CEO letter raises the concern for regulatory authorities of whether the content of the CEO letter should be audited, since any numbers presented in the management report have to be audited in Portugal.Originality/value– To the best of the authors' knowledge this is the first empirical exploration of the characteristics that explain why companies publish a CEO letter. Mimetic and normative isomorphism is revealed to be a potentially important influence, since there is a tendency of companies audited by Big 4 accounting companies, and with foreign subsidiaries, to publish a CEO letter.