A concomitant of the corporate integration of sustainable development is that companies even make public reports about their relevant activity via communication channels, as they expect to see some short or long-term competitive advantages. This thesis focuses on the content and the audit of sustainability reports. Assessing the information content of these reports and trying to figure out if the producers of these reports can actually be considered socially responsible. The thesis gets a nearer view of the quality of the audit, based on the stakeholders’ preferences. The basis of the dissertation was the sustainability and corporate governance reports of the companies listed on the Budapest Stock Exchange. The research has led to prove that the audit of sustainability reports has an increasing relevance among the stakeholders, even though its audit cannot lead to reasonable certainty on the account of the complexity of the used data and the subjectivity of the opinions. Having analysed the sustainability reports published in Hungary, as a conclusion the audit of sustainability reports creates value. It creates value since reliable and authentic data are more likely to be integrated in corporate decisions. No sustainability results can be achieved without a reliable reporting system, which also has a multiplier effect. The external stakeholders, including primarily investors and analysis experts, can rise to a higher level of trust and make better decisions in line with the company, in so far as they can have access to an audited sustainability report, along with the audited financial statement.