In recent years, companies have been introducing the concept of sustainable development in their operations in order to respond to the challenges that the whole world is facing. Sustainable development is a term that implies providing future generations with the same quality living conditions as today. Sustainable development includes three dimensions: economic, environmental and social. Companies operate in an increasingly challenging environment, and as a result, they are no longer oriented solely on profit, but want to create a positive reputation in a way that cares for the environment, the society in which they operate, and the economy itself. The importance of sustainability is also shown by the fact that the European Commission passed a directive obliging large companies to publish non-financial information from 1 January 2017. Such a decision led to the development of integrated reporting in which companies combine financial and non-financial data. In the paper, research is conducted on a sample of nine out of ten companies that are an integral part of the CROBEX10 index. Some companies started with non-financial reporting even before the introduction of the obligation. As a rule, companies that started with earlier reporting have more extensive reports and a greater representation of the GRI standard according to the three categories. Furthermore, the impact of sustainability, which was measured according to GRI standards by comparing the number of published topics per company and the total number of topics for a particular category, on the company's performance was examined. According to the results of the statistical analysis, there was no statistically significant impact of sustainability on the return on assets and profit margin, while the impact on the return on equity was significant.