This paper seeks to investigate the practices of corporate environmental disclosures of the IBEX 35 Spanish firms on their websites. Three areas are studied: (1) the disclosure of non-financial environmental reporting; (2) the disclosure of financial environmental reporting; and (3) the analysis of some aspects of the corporate websites that, in our opinion, could affect the availability of the corporate environmental reporting. The main findings of this paper are: (a) environmental disclosures made by firms present a slight concentration of the data; (b) the compliance of the standards of GRI guide is a key variable for non-financial environmental disclosures on the internet; (c) financial environmental reporting disclosed in the financial statements is quite limited, and (d) there is a need to link non-financial environmental reporting and financial environmental reporting, so that the user of the information can have a greater detail of the influence of environmental concerns in the management of the firm.